I have a few sure fires, I like the saint minimus for a headlamp, the x300 for weapons, and the two lights below that are LED and have different pieces so that they will accept either a single AA battery or a Single 123A battery. I usually carry both lights, one with an AA in my pocket all of the time and the other with the adaptors in my pack/gobag.

http://www.batteryjunction.com/oligh...nsformers.html

http://www.batteryjunction.com/sunwa...r-ti-plus.html

http://www.batteryjunction.com/sunwa...-extender.html