I asked Rob Silver about this, who is my go-to when I need information about mushrooms. I don't think anyone is more up to speed on the industry than him. He noted that no psilocybins are currently available for veterinarians as yet, so there is some legal exposure there for those that utilize them.
Rob mentions that "a lot of people are cultivating it one their own, its fairly simple and there are companies out there that sell grow medium, and others that sell spores", in case you want to avail yourself of some and are willing to take the above risks
Steve