flapper
I bought a bianch current model nylon GI flap holster a while back for SIG P220 and my glock 20 rides well in it. I bought the thumb break adapter too, and when the urge strikes, fold the flap under the back of the holster and simply use the thumb strap for retention. The pistol, a dbl mag pouch w/ a mag and a multitool, sometimes canteen, and somtimes a large fixed blade, ride on a GI web belt.
Fully loaded, I sometimes use the suspenders that came w/ the belt. This is a field rig, of course.
I have been completely satisfied w/ the Glock factory concealment holster, but it sounds like your not interested.