One possible means by which to aquire the beneficial fungus, is to locate a thriving speciment of the heath family out in the unadulterated wild; such as wild cranberry, blueberry, huckleberry, azalea, rhododendron, etc... dig down a little bit, just inside of the plant's dripline, to see if any of the fungus can be found. It will be creamy-white to khaki in color and growing from the plant roots. It is extemely delicate...
I have yet to look into a source for the powdered material for inoculation. Something I ought to do. Especially when talking of more than just a plant or half dozen to be inoculated.
More information than you'll probably ever want, lol: