Where to find a small form factor 12v Battery?
I am looking to build an LED light that can be powered directly by a 12v source or use an internal battery. I expect that the fixture form factor will be about 4" in length by 2" to 2.5" in width and no more than 3/4" in depth. Internally, it needs to fit two LED units (each draws 0.1-0.2amps and only one would be on at a time) that are 1"x1"x5/8" each, the inside component of a single pole double throw waterproof switch and the remaining space for batteries. I would like to fit the maximum amount of available capacity as possible in as small a space as possible. I am looking for battery suggestions - small form factor, 12v, preferably available via a regular source (i.e. don't have to be special ordered from China), low self-discharge rate, ability to withstand temperature extremes (specifically 120F-140F degree heat). I'll consider wiring up batteries in parallel and serial to get the charge depth and the proper voltage. Any thoughts? I looked at A23 12v batteries and 2CR-1/3N 6v batteries (wire in serial) but I'd like to find something with more available capacity. Also, I'd prefer a non-toxic battery, but will consider lithium, and the ability to be recharged would be a big bonus. I'm guessing there's nothing out there that would give me enough life to be happy, but I thought I'd ask.