I too was shopping around for a new keyboard recently and did not find a single one that was specifically advertised to support Panther. That's probably just because they were all manufactured prior to the release of OS.X.3; most Macpatable drivers do actually work in OS X.3, as you correctly surmised. I downloaded the one for the Elite and it installed fine on OS X.3.2. Nifty preference pane, too! Of course, without the actual keyboard I couldn't test it further, but the documentation that came with it said that it requires 10.1.2 or higher, so you should be all right.
(Incidentally, I ended up purchasing the sort of dated looking iMedia from Macally, because
Amazon was offering it dirt cheap-- no tax, free shipping-- and I wanted a wired keyboard for the USB hub and power button. Picking it up from UPS today.)
Good luck with your purchase, and enjoy Panther!