if you are willing to spend a bit heavily i would recommend picking up a cadpat drop leg holster from
http://www.dropzonetactical.com/hols...opholster.html
the kit is 100% authentic and is used by many canadian troops in afghansitan at the moment. i know its not cheap but i use mine with my gbb and i love it, the quality is there to support that price. as well the company supplies vests including a modular vest that can be set up to look very similar to the current issue. i know he had one set up that way the last time i was in the shop. just be warned that it doesnt come cheap.