hmm- there are two kinds of sew-ons, as far as the nice, sparkly glass ones go...

the 'rose montee' that's the classic flatback in a silver cage with an x-shaped channel on the back to sew through

and the kind with holes in the rhinestone itself, that's either stitched down like a sequin, or tacked on with a seed bead like a button.

I've bought most of the ones that I have off ebay, there's one guy who only takes checks, but has wonderful vintage ones at pretty good prices,

www.bconklin.com

is also a name I recognize from Ebay as a good solid dealer.

you don't need a setter unless you're doing hundreds of them, really- I've set them myself with the little clamps- you just bend the prongs over the stone with the back of a spoon, or a burnishing tool, I bought that newfangled plastic one from the craft store, and it was so bad I returned it in disgust.

if you're doing LOTS of them- consider hooking yourself up with the hotfix- it's a cross between a glue gun and an embossing/woodburning tool, and lets you hot-glue flat back stones preety fast.