http://www.alpkit.com offer one of the finest budget head torch on the market.
The Gamma LED Headtorch offers around 80 lumens from a single XPC Cree LED but also has the addition of green and red night vision LEDs.
I'd had used my head torch on a lot of trips for a number of years but unfortunately on one particular trip the battery clip door latch broke off when I was replacing the battery and rendered the whole unit useless so I've come up with a universal fix which should give you a little bit more use out of the left over torch.
The original unit was powered off 3 AAA batteries equating to 4.5v
I did a fair amount of research into alternate battery clips and batteries and in my opinion this was the the most efficient and cost effective.
Although my solution isn't technically kosher it works and will get you a little more life out of something that is bin-bound.
Parts & Tools needed In addition to a broken gamma head torch
1x Emergancy Mobile Phone Charger (EMPC)
1x AA Battery
1x 2mm Jack Plug (Several packaged with EMPC or you can buy separate)
Wire cutters/ strippers