Just got one of these:
http://www.bestofferbuy.com/uniquefire-l2-cree-xpgr5-5mode-320lumen-led-flashlight-black-118650-p-53094.html
Decent run time, very compact and not too heavy for use on head. I’d recommend it – was using another DX torch but it was too big and heavy for use on the head – it’s now on the bars in a complete overkill double-P7bar setup to go with the XPG on the head. Just got in from a quick pootle round Woburn in the dark and that lot combined with the reflective ground due to the snow meant there was plenty of light – especially for the speeds I was managing in the snow…
Whatever you get, check weight before buying.