The black market should service him! If he asks around, he may discover a few underground shops scattered throughout the Pavillion who will help him if he seems in dire need of it. These places often smell suspiciously like wet dog and fur. They do not appear interested in questioning him nor are they surprised by his concerns. They are not strictly illegal -- they're simply not regulated and can sometimes do things on the side that are illegal, but he won't get in trouble just for purchasing from them.

They will also not be able to explain very well how these concoctions are made. He'll simply have to trust them. They come with varying degrees of effectiveness depending on price and quality. They can be pills, a powder, an injection, or anything you want. He might find something that works perfectly right away, or he might take time before he locates the right balance. You can decide based on what you think is more interesting.