Since my last post, I have found a liquid extract that includes a large portion of agaricus brasiliensis. The product is MyCommunity by Host Defense. (In double checking information for this post, I notice they now sell Blazei Extract, which contains only agaricus brasiliensis. I might order some.) Again, I do not use it orally. I use it topically, as needed. It stretches a bottle out pretty far.
There is another product in the US market, Lipopo by Umeken USA. The primary active ingredient is fermented wheat extract. It is kind of (ok, very) pricey, but it is the result of nearly 30 years of study, so if you think you need it, it is worth it. If you take it as a sublingual, rather than just swallowing the pills, it might be more effective.
If you are a home brewer, you might be able to approximate it with some experimentation. You would start by making wheat gluten, but instead of tossing the rinse, you process it in a centrifuge, then take the supernatant and culture it in a fermentation tank. The trick is finding the right food to feed the P. agglomerans, without feeding stuff you don't want. A good brewer could figure it out. You will also need some bio lab experience to do assays to know if you are getting the right things to grow -- or maybe just drink a lot of wheat beer or wheaty kvass.