Oxalic acid is commonly available at most hardware and home improovment stores in the US in small amounts under the name "wood bleach." To purchase amounts in the range you ask for would likely require establishing a relationship with a commercial chemical supply house such as Baxter or Fisher Scientific. In major metropolitan areas there may be local suppliers as well. In order to do this you will likely need to proove to them that you are an established commercial operation with a valid need for the chemicals. Because of liability concerns most commercial chemical supply houses are reluctant to deal with private individuals these days.
