The ALG 6 Second Mount has an ever growing list of holster makers who are bending kydex for it. The latest that I have seen is Vigilance Tactical. They are making both their Sentry6 and Nocturnal Sentry6 holsters for Glocks equipped with the 6 Second Mount. The options for these holsters are nearly endless and include things like accomodating a threaded barrel, adding a thumb break, 5 different attachment hole patterns, and more.
Check out the 6 Second Mount holster options at Vigilance Tactical. Check out our review of the 6 Second Mount.