They were all over the place at the 1500. DSG Arms online also has them, and Brownells seems to get large shipments in on a regular basis (backorder them; they don't charge your card until the order ships). Locally, I dunno.
There was a guy at the 1500 that had Green, Black and Tan mags in the wrap for $16. He had cases of them. Anybody try the SS mags that were coated black?