Is this a unicorn? I've landed my dream pistol, the above-mentioned USP Expert 45, and have since given it a couple of finishing touches (only somewhat-relevant one for this topic is a Dawson Precision fiber optic front sight). I'm looking to get a GG&G mount for a light, but this setup needs a holster.

I've got a Streamlight TLR-1 and TLR-1HL already, but wouldn't be averse to getting a Surefire X300 if needed to fit an existing holster setup. Thing is, most USP holsters that I've seen are for standard USPs, and haven't found any holsters for a GG&G + mounted light. If I'm throwing my entire wish list out there, level 2+ retention would be preferred to a simple friction-fit.

Would I have to go custom?