I wear NODs, a conventional headlamp won't mount with them. (unless there is a mdoel where the head can swivel 90 degrees to the left/right.)
For a helmet mounted light I use a surefire E1E, 2.2 oz and 90 minutes of burn time, clicking tailcap, attached by velcro to the non-firing side of my helmet. Can swap it out for a M1 infrared illuminator as needed.
Idea stolen blatantly from BL and adapted for white light/medical use.
Dan