It's stupid easy to grow yer own and I do it every year. Just takes some time.
Alliums (onions, garlic, leeks, etc.), have a very strong affinity for mycos and vice versa.
What *I* do is, every fall make up 6-8 cf of fresh mix, or however much I might need for next year. This goes into 5 gal buckets with 4-5 cloves of "Music" and "Georgian Fire" garlic inoculated with MycoGrow Soluble. Then overwintered and harvested early the next summer. Plant on Halloween, harvest on the 4th of July, is the general rule of thumb. The roots are chopped up and added back to the mix. The entire batch of soil is inoculated.
Another way is to inoculate Leek roots, grow for however long, dig up, harvest 1/2 - 3/4 of the roots and replant the leeks. Use the cut roots to inoculate mix or plants. The Rodale Institute has the info on this method.
I mean, this stuff occurs naturally and spreads naturally from spores when the myco's fruit (mushrooms). Man has just very recently got involved. Myco's have been around for eons.
Wet