I saw the Clip-Its at the Blade Show---they work pretty well, and come in two sizes. It converts a belt-loop item or a strap into a metal clip. Good suggestion!
Rip Off belt clip stuff has a great, strong clip that "locks in" over a lip on the inside bottom of the clip and stays very secure(it's hard to describe, but it works well)on a belt.It's also easy to release one handed when the time comes. I've been using one as a Star Tac cell phone holder and it keeps the phone nice and protected from the elements.
Depending on how big a pouch you need, materials quality, and the clip option, I've seen some pretty good stuff at Campmor.com, EMS, and REI, too.