There is a plausible way in which Bob Lazar's element 115 could be synthesized. However, to full grasp the content of this post, you'll need to do your own digging and research, because there's a ton of information in the literature about this phenomenon if you're willing to do the work. If you are willing to dive in and look at the broad scope of information going back a century or more, you'll realize that the bulk production of virtually any element is feasible by a well funded Special Access Project that has been secretly working on the technology for decades or longer.
A decent number of people have heard about "cold fusion" or what some people today call "LENR." LENR stands for Low Energy Nuclear Reactions. Basically, utilizing this phenomenon you can produce copious amounts of energy via less than fully understood (at least in the declassified world) with USUALLY far, far less radiation than would be produced if a "hot fusion" method was used — slamming the atoms together at ultra high energies.
There are many variation of cold fusion. Some utilize an adsorption/absorption process to get hydrogen or deuterium into a metal lattice (palladium, nickel, titanium, etc). Both gas loading and electrolytic loading can be utilized. These systems do indeed work. But if you don't utilize something I'm about to talk about, the excess heat effect can be more challenging to produce.
Next, there are plasma based systems (some of which are hybrids that use powder as well) that ionize a gas composed of hydrogen or deuterium and often other elements (such as lithium or nano-particles of various metals). Some plasma devices utilize an instant burst of plasma such as pumping a massive amount of current through a thin wire until it suddenly vaporizes. Others utilize a pulsed glow or arc discharge between two electrodes in a sealed container. There are several other varieties as well.
What it seems to all come down to is if you are able to dissociate molecular hydrogen (two hydrogen atoms chemically bonded together) into atomic hydrogen (single hydrogen atoms) and make them collide with atoms of other elements you can induce non-traditional nuclear reactions. I should also mention that in some cases (NOT ALL) electromagnetic stimulation to both dissociate the molecular hydrogen and stimulate the reactions between atomic hydrogen and other atoms is extremely helpful.
Now, to try and bring this all together, the result of these reactions are excess energy (in multiple forms), often some small quantity of radiation (not always), and the TRANSMUTATION OF ELEMENTS. My understanding is that in many of these systems, if you make atomic hydrogen and a target material interact the target material will go UP in number. I'm not saying this is always the case. But it is a common trend. This is NOT speculation. Such transmutations and ISOTOPIC SHIFTS have been documented repeatedly in all sorts of cold fusion systems. Interestingly, the RUSSIANS have a LONG history of performing such experiments. And, thankfully, do to the fact that most of the "mainstream" non-classified world considers such experimentation total bunk, hundreds and hundreds of such Russian papers are available online if you are willing to dig. In their experiments, they have produced all sorts of transmutations including rare isotopes and precious metals.
I suspect that there are Special Access Projects in the United States that have mastered this technology. Compared to building a Fluxliner, it would be far cheaper and simpler! To produce a few hundred pounds of element 115, they would need to produce a reactor that could subject feedstock of lighter elements to atomic hydrogen under carefully controlled electromagnetic stimulation (magnetic and electric). Letting the experiment run for months or years, I suspect they could produce copious amounts of element 115. By controlling the energies and feedstock, they could produce only a STABLE ISOTOPE.
I suspect that's why 115 is so secretive. It's existence in bulk would PROVE that the government/military mastered transmutation a long time ago. They would not want such technology to be released, because it would give every nation on the planet the ability to produce any element and isotope they desired – even those that could be used for nuclear weapons or exotic propulsion systems.
Why do you think LENR was so viciously attacked in 1989 by the hot fusion crowd?
To give you an idea of a super crude system system that could plausibly produce element 115 (there are more sophisticated ones) imagine a metal cathode of a target material. Since we're talking about a govt/military lab with unlimited black budget money, this could be a LARGE cathode with high surface area (LENR is mostly a surface effect that doesn't penetrate more than a couple microns). One or more anodes would surround the cathode and they might actually be on a platform that would allow them to rotate or move. Hydrogen, deuterium, or tritium could be pumped into the chamber and then an exhausting series of electrical discharges could start. Each discharge would ionize the gas and slam protons (atomic hydrogen) into the cathode. Slowly, over time, more and more element 115 would be produced on the cathode. Additionally, the polarity could be reversed to produce additional effects. After a period of time, they could scrape the surface layer off the cathode (only a tiny amount), separate the ultra heavy "stable" 115, and let another layer of the cathode be bombarded. When they are done, my guess is that they would lightly sinter the resulting 115 into one large mass for transport to Los Alamos (a bunch of small containers would be a larger security risk and handing powder can be messy).
I know this post has been a little vague. I could make it ten times as long. But to be honest, I don't feel like writing a full, detailed report. As I've said elsewhere on here, I'm burnt out with ufology in that NO ONE seems to be active in pushing for disclosure. Even the TTSA association seems perfectly content to drag everything out while not publicly urging individuals such as William McCasland of Wright Patterson to come forward and share what they know.
(One little note I would like to add too. Bob Lazar mentioned that they bombarded 115 with atomic hydrogen to produce anti-matter particles that seemed to fuel the propulsion drive. I may have an explanation of this. Repeatedly, in virtually EVERY type of cold fusion or LENR system, the bombardment of targets with atomic hydrogen produces not only conventional forms of radiation but also STRANGE RADIATION. These STRANGE radiation particles are truly bizarre because they behave like no known particle, can transmute materials, leave totally strange track marks on various media (glass, mica, metal, x-ray film, etc). No one really knows absolutely for sure what they are! Because of the fact they seem to deposit HUGE amounts of energy on target media (gigaelectron volts instead of the megaelectron volts carried by most particles emitted in nuclear reactions) I think the scientists at S4 could have guessed that they were anti-matter particles. In fact, it's not too far fetched to think that they may be some strange conglomeration of ordinary matter and some exotic form of matter we don't know about. These particles could have been "caught" by the gravity emitters and used as an energy source.)