From reading the info on ETS and this forum, I have a Photon II. I've had no battery problems yet (i've had it about 5-6months). Quite pricey (and in theUK difficult to get hold of)I've not tried any of the alternatives listed here.

What ever you choose, make sure it has an on/off switch, and doesn't rely on you pressing the button continuously to keep it on. Makes life easier.