There are many sources of information on the fly agaric that are speculative at best (Christian Rätsch, R. Gordon Wasson and Carl Ruck come to mind), but here are a few good ones:

As to procuring your own Amanita muscaria, of course foraging for them personally is always best, but if you don’t live in the right climate, they can be found online in several places, my favorite being Bouncing Bear Botanicals.