The ‘Espresso Oyster’ patch seems more worthwhile. Here they admit it’s just sawdust spawn which they recommend you mix with coffee grounds. They also say that hardwood sawdust is fine and shredded paper will work in a pinch.
So that’s a big old plastic tub from WalMart (where else would you go for plastic?) with a 50-50 mix of oak planer shavings and coffee grounds. It ought to work fine, but may take longer than desirable to fruit because of having so much substrate.
If it works, we’re totally set for next summer though. We have coffee and wood chips enough to grow these things by the acre.