It used to be sold in cardboard tubes of just crystal powder but now I can only find it as a part of something (sold as a tinted wood bleach or in a liquid form mixed in with something like Thompson's Deck Seal.
I should have said I'd like to be able to soak a half a bike frame at a time. I want to buy 4-5 pounds without breaking the bank so looking for bulk source.
Wondering if anyone knows a good source?
...are you sure you need 4-5 pounds ? Check out how much youi will need to mix with water, in order to fill your backyard tub of it. Then if you have the space and can cover your soaking tank (which I recommend), you can simply leave the stuff over in a corner somewhere with a poison hazard label on it.
I think I only bought maybe 8 or 12 ounces of the dry stuff in a package at the hardware/paint place, and I only used maybe half a cup of the stuff to mix up a huge plastic storage bin full of it for a soaking tub. You buy those at the Home Depot with a good, tight cover. Ask for "wood bleach" as you call around. The more of the stuff you mix up, the more you need to neutralize and properly dispose of afterward. The stuff is toxic, highly acidic when mixed for soaking, , and not at all benign. Neutralize with large amounts of baking soda or another alkaline agent before disposal.