There are (were) only two third-party suppliers, Plinker Tactical and ProMag. Although both brands can still be found on shelves occasionally, both companies have ceased production and sales due to being sued by S&W for patent infringement.

That said,if you can find some ProMags, buy them as they are top notch. Plinker Tacticals, on the other hand, run the gamut from acceptable to trash with no discernable way to find out which before buying.

The only 15-22 mags currently in production are those from S&W.