Aside from the suggestions Barry made, there are a handful of other places relatively nearby.
* In downtown Roswell, Go With the Flow
is primarily a canoeing/kayaking shop, but they have (or had last time I was there) a modest selection of Innova discs, mostly in premium plastics.
* The Play It Again Sports at Alpharetta Highway (Hwy 9) and Mansell Road also sells both new and used discs, with new stuff from Innova, Discraft, and a variety of other manufacturers.
* Dick's Sporting Goods and Sports Authority at North Point Mall both have a very limited selection of Innova discs. Last I was in Sports Authority, they had recently restocked, but they seem to only ever re-order the same discs they've been ordering for years -- a lot of Vikings, Sidewinders and Roadrunners, Sharks, Aviars, Birdies, Stingrays, Wolfs, etc., plus Innova DX and Champion starter kits, etc.
Among the various sources, Disc Caddie and DiscStalker, and to an extent PGA Tour Superstore and Play It Again Sports, have been active supporters of the local scene, providing tournament and tee sign sponsorships, donations, etc. It's always good to support the businesses that put something back into the sport.