at a local store. Ace Hardware, to be specific.
Understand, I'm glad to have found it. I just wish I'd found it a week ago. When I was in this store and asked, and they said "We don't carry that".
Just happened to be passing by on my way home from work and decided to check the plumbing supplies(just in case) and there, among the other drain openers/cleaners are 16oz. bottles of 100% Lye.
Moral: unless you KNOW the guy, and are certain he KNOWS the stock, go look.