Home depot. Found mind, strangely enough, in the same aisle as faucets and showerheads and stuff (but on a different shelf, though, so it wasn't
too weird).
$7 got me a 5-pack some time around last December... I've only burned through two since then. I don't use 'em every day, though.
Maybe possibly, I'm not sure.
I know a guy that knows a guy. Left hands are goin' for about 7500, righties an even 10. If you want a pair I might be able to get you a 2-for-15 deal, but don't get your hopes up.