In reply to girlymonkey:
I have the lenser torch that girlymonkey mentions. I have tested it out for real after a late finish in the Northern Corries and am very happy with it.
It has a rechargeable battery but I also carry some AAA's taped together in the right orientation in my sack. I would imagine you could easily source an extra rechargeable.
I've had it for over a year and still haven't had to recharge it!