As mentioned above you can go with a 6" BladeTech holster or just hit end of a 5" holster with a heat gun an open it up. My 7" long open gun goes in my regular holster with that technique. To tip just sticks out a bit.
I've got 2 bladetech's that I really like. I'd go with the BlackIce version if available. Good enough retention for 3 gun and can be loosened for USPSA.