Never done this sort of thing before, so I guess it would be a case of soldering an old battery cartridge with wire's so I could get a direct feed out the back (or wherever), and put a connector on there to hook up whatever I wished. Can't be 'that' hard.
BTW, just found 3x AA headlights on ebay although it's it's only 260 lumen
Will need to confirm it's AA and not AAA though.
UPDATE: Jut ordered this 4x AA battery holder for an experiment. http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280626489247&ssPageName=STRK:MEWNX:IT
Would love to lose the extra 0.3v (from 4.8v down to 4.5v for safety), but don't know how to do that?
EDIT: Totally off-topic, but only just found out that with P7 LED's, the current best 'bin' to go for is D-bin. It get's 800-900 lumen where C-bin only get's 700-800 lumen apparently. (Back on topic of waiting for all my little goodies to turn up lol).
and back on topic: Think we could get teh LED and star circuit out of this for £7.83? http://cgi.ebay.co.uk/Ultrafire-CREE-XR-E-R2-5Mde-LED-Spare-Bulb-6p-G2-D2-G2-/220597567182?pt=US_Flashlights&hash=item335ca3bece