I bought several Nebo neoprene holsters from Batteries + Bulbs when they were on sale for $3 each. They depend on elastic tension to hold the flashlight and they do stretch out some, but as long as the head of your flashlight is sufficiently large and you insert it head-down, the holster will hold your light securely. The belt clip is weak, so sometimes when I grab my light, the holster comes with it off my belt.
They're inexpensive and functional, but I would consider them a last resort kind of thing. Use them if you can't find anything else better.
Solarforce has 2 or 3 holsters available for their L2 lights for around $4 each. The two I have have velcro, but the velcro is just to keep the flap from flapping. It is not required to retain the light.
Finally, I've had good luck replacing velcro with magnetic snaps in the past. You can find kits at hobby or fabric stores.
--flatline