Any of the nylon tube style holsters made for common duty lights should work, if you just want something simple. I have a Blackhawk one made for the SF 8AX/SL Stinger that has a removeable flap, and works fine with the UltraStinger and a Leef 2x18650 body+KT2 turbohead.
If I wanted a serious piece of gear, like something made to fit plus full flap and fastex buckle, I'd be contacting John Willis, as has already been suggested.