Lou Alessi makes a great ankle holster. He doesn't have a website but lightning arms retails his rigs.
http://lightningarms.com/products.htm
Josh Bulman also makes a nice rig. Josh is a protgee of Lou's. I have only had the chance to eyeball a couple of Bulman's rigs but owned an Alessi a couple of years back. It was a top notch piece of gear. Sold it to a friend and have regretted it since then. Lou speaks very highly of Josh.
http://www.bulmangunleather.com/ankle.html