I don't own one but given the grip angle difference, I'm doubting flap holster for a MK IV std will fit a 22/45 well. I'd me more inclined to shop for a 1911 full sized flap holster and see how that fits. p.s. I'd be buying it from a vendor that accepts returns as well. FWIW, there are quire a few on Ebay including one from Barsony which looks like it would work well. Just search "flap holster"