Another way to mount optics on your pistol is to use its under rail with a product like the Kinetic Concealment CompRail Combo which already comes with an RDS... "This is a combo kit that includes one RD-01 Red Laser Dot Sight and one CompRail System. This combo kit is designed for the 3-Gun Shooter or anyone wanting to do some handgun target practice. The kit fits all 1911 pistols with rail, Sig 250, Smith and Wesson M&P Full and Compact, and Beretta 92 and 96.

Check out this review by Booligan Airsoft of the Kinetic Concealment Red Dot Sight and affordable optic that can be used with real steel guns and can fit any Mil-Spec rail system... "Real steel accessories at Airsoft prices tend to be a little hit or miss, but this compact red dot sight from Kinetic Concealment seems to be a hit so far!"