I've never been able to find a holster for my Sigma and the Streamlight M4 Tactical Illuminator It's snapped on when it's in my nightstand. Fumbling around for my pistol and my Maglight is asking too much of me at 4 a.m.

In the winter with an overcoat I use a Blackhawk Serpa CQC paddle and when wearing anything lighter a Don Hume IWB Model H715.

You might be able to get away with a very large generic nylon holster, but I'd imagine it would be too large for concealed carry.