Georgia Arms and
Bitterroot Valley both list 10mm. I have purchased from Georgia Arms before, but have never tried BVAC. I would have purchased from BVAC for my second 1K, but I started handloading.
Double-Tap also makes some good ammo. My carry ammo is double-tap, and I try to shoot about 300-500 rounds per year of their fodder through my guns.
Don't start handloading. It is just as addictive as shooting, and before you know it you will be casting your own bullets too. I can shoot 10mm, 357/38 and 44 Mag/44 Special for about the same price as I can shoot .22.