Well, I finally found some of the stuff, and in the interest of trying to help others who are also trying to find some I thought I'd post some pics and where I found it. And I've been looking at quite a few places. A lot of the times people in the stores I went to had no clue what I was talking about, and being way past due for a haircut and a shave they were probably wondering what I really wanted it for. Anyway....
The local Home Depot stores around here no longer carry it, I finally found someone who said their distributor just stopped shipping any to them for whatever reason. I did find some at a local Sherwin Williams paint store, but even there one clerk had no clue and the other clerk on duty knew what it was. They had two 12ounce tubs left at around $9.50 each. Okay, hoping to find a bigger tub I checked one more place the Home Depot lady said to check, the nearby Ace hardware store. Got to Ace, went to paint, found someone who looked like they had a clue, and they took me right to it. They had over twenty 12ounce tubs on the shelf at $8.50 each so I got one to try it out. I had also stopped at the local woodworking store, WoodCraft or WoodCrafters I think, and all they had was a two-part liquid wood bleach with something other than oxalic acid in it.
So here's a couple of pics of what the tub looks like so any of you who haven't been able to find any will know at least what one brand looks like. I may mail order a 7 pound tub from some online store I found but will give this stuff a go first. I might have to wait though because I don't think I want to use this in the basement near the gas furnace, and the garage is currently below 4degF so anything I put into the solution might just freeze, and I don't think that would be a good thing.
Oh, and any guesses from you experienced users of this stuff how it might work on the Schwinn seat springs on my old 1967 2-speeder? I assume I don't want to soak the seat cover in it and will probably wait for warmer weather to try it out. First things I'm going to experiment with are some steel cranks and chainrings. Anyway, here's the pics of the stuff in the tub.