A few years back I purchased a lifetime supply of lime wood from a specialty wood supplier. I've been running these airstones for years in my skimmer replacing them every two weeks. I'm going to upgrading to a beckette style skimmer with a new tank and won't have any use for wooden airstones. J&L sells 4" stones for 1.49 and I'm willing to sell the 3" variety for .45 ea. with volume discounts.
Let me know if anyone is interesting. These stones produce nice fine bubbles and you could gang them together to get the amount of foam you are looking for.