I thought that I left a response to this. Here goes again.
For MnO2 or the WWII color ZnO2, check your local pottery supply stores. Potters use both chemicals for glazes. The stores have bulk amounts cheap. Expect to pay much less than $10 for 4 pounds each.
85% Phosphoric I got from Triple-S chemicals in CA. Shipping was as expensive as a gallon of acid.
You may want to try local brewer's supply stores which sometimes carry qt quantities of phosphoric for dissolving brewer's stone.
Good luck.Originally Posted by machman