I use one that I picked up at a sporting good store (EMS or somewhere similar) a while back. I think it's the Jakstrap (it matches the picture of the original but I can't find a label).
I had my Arc AAA with me when I bought it, so I tried it with a few and found one that was a good fit for the Arc AAA with both loops (it was designed for the minimag, but there was some variation in loop size).
It's a nice system with two loops. One faces straight forward, one angled down, and you can put the light through both loops to get a shallower angle down. I use it with my Inifinity Ultra (a tight fit) to read at night, but next time I go camping I plan to use it with my Arc AAA as my primary camp and night walk light. I found that an Arc AAA is about the right amount of light for walking at night (on decent trails) as long as other people aren't killing your night vision for you. Having a headstrap means I don't need a dedicated headlamp which simplifies things.
Next time I'm in the states I'll have to check out the Niteize; meanwhile, I can recommend the Jakstrap, but I'd recommend buying it in person and trying it out with your light of choice to get loops that fit well, especially if you plan to use an Arc AAA or similar sized light. They are elastic and will take a larger light, but the elastic is tight and I'd recommend getting one that fits just right. Mine's perfect for the Arc AAA but a tight fit on an Infinity.
- Russ