High cap aftermarket mags for Sig P226

I recently bought a used factory hi cap mag for my Sig P226. After it worked great (of course), I was thinking of getting another hi cap, this time a "less expensive" one. I was thinking of getting a Promag, since it comes with a lifetime warranty. My brother-in-law bought an aftermarket (not sure which brand) and it didn't work. Anyone who's had experience with aftermarkets for Sigs, let me know what works. And don't say Mec-Gar, I know they work, but are as much as factory mags.-Marcus