I reload, but started shooting 10mm before I did. I can second Georgia Arms as a good source of mid-range ammo. And, in case you ever get into reloading, they use Starline brass, which is great stuff - so save it. Or send it to me!
I used to find good deals on Prvi/Partisan/PPU ammo from Palmetto State Armory. That's very downloaded stuff, less than max .40S&W, if the chrono results I've seen posted are to be believed. That said, it's great stuff for pleasant shooting that won't put much wear and tear on the gun... and it always fed very reliably for me.
I started rolling my own before I tried it, but I read good things about Underwood for full-throttle 10mm. And, at least last time I looked, he was charging for 50 rounds what DT or BB were charging for 20 or 25. So when you're ready to kick the snot out of yourself and your gun, that may be the way to go.
Hope that helps. BTW, 10mm is a great cartridge to learn to reload.