I've also read good things about this place for cheap mags. Joe's 1911 Mag Mania | 1911 Magazines At Warehouse Prices
I personally would go with Wilson, Brown, Chip McMormick in that gun. Watch for fake "GI" mags. Lots of imitations around. I even saw a fake Colt stainless mag today. Crimped bottom 4 way and real poor quality follower.