I have been using MecGar magazines since I bought my M1991A1 in 1995 - they work, and have NEVER failed me! MecGar is a subcontractor for many gun manufacturers and makes many OEM magazines.
I have a Wilson and a McCormick - they are excellent - the MecGar is just as good and half the price.
I once made the mistake of ordering a half dozen 'no name' magazines from The Sportsman's Guide. Two failed catestrophically IN the pistol! The welds on the floorplates broke, and the mags self-destructed. I threw all six away after stomping them flat. I learned real quick to "buy the best!"