Try an Auto parts store, they usually have 1-4k. I also have bought 800-6k half sheets pack at Wall Mart, in a locked cabinet, in Automotive Dept. A good Ace Hardware has full sheets, up to 2k in stock. Ace also carries Crocus Cloth for a Satin finish. Not all Ace stores stock the same stuff.

The higher grits and Micro Mesh last a long time, I buy Micro Mesh in pads and paper locally, from Hobby Lobby.