i’ve got some Q5 2AA torches from dealextream. With a bit of drilling, soldering and fiddling they make 240lumen 58g lights. I usualy run them off a homemade 3V battery pack in the cammelback. Gives about 1 hour of light per AA battery (so upto 8 at the moment).
Got 4 torches as well so can generate about 950lumen and the 250g weight is still fairly small, especialy as you can spread them out so it doesnt feel like youve got a pendulum on your head, 2 on top, one above each ear.
Total cost is knocking arround £70 at the moment.
not so great bar mounted as the beam is a spot that fades away to the edges, great for looking well down the trail, not so great for seeing round corners when bar mounted.