Hmm an interesting problem, I was able to think of a few solutions to it though. The first and most simple being the Pantac MP7 holster if you don't mind that. If that doesn't float your boat then I thought of two other solutions for webbing gear.
An S&S weaponlink (there is a repro version too) could be used either alone or in conjunction with a one point. I'm not a fan of repro kit but in this situation it may very well work fine.
The other solution is to do what you are doing now but just use the First Spear Weapon Retention Catch in conjunction with the one point to hold the gun down. No velcro like a normal weapon catch either so that issue is solved.
