I found eight cans of the precious paint at the Wal-Mart on 135th in Olathe. This is apparently the only place in my area that reliably carries it, because I've checked every other hardware store and Wal-Mart around here. At least I should have enough to paint most of what I need, and I know where to get it now if I run out in the future. I also cancelled my online order since the stuff from Wally World was two bucks less per can. Whew, at least that frustration is over with.
P.S. I actually called Rustoleum to see if the hardware store guy who claimed that my paint was discontinued was right or not – the customer service lady just laughed and said "oh no, we're still making tons of it." So nuts to you, Westlake hardware on 23rd in Lawrence.