Amazon.com has the Streamlight 61702 Bandit [amazon.com]
rechargeable USB headlamp on sale at $15.88 (lowest ever recorded price). Black color with white LED, rechargeable lithium battery via microUSB.
Spec'd at 1.3 oz with the strap, 2 hours at 180 lumens high output, 9.5 hours at 35 lumens low output. IPX4 water resistant (NOT WATERPROOF).
I'd researched USB headlamps last year, and this was one of my top choices for a lightweight, ultra-simple rechargeable unit. Usually goes for around $20 shipped. Should be a great unit for close range work, but I've read CRI is not very good. If you need waterproof, this is not your light. Also, lithium polymer battery, so YMMV if you plan to store this in hot environments.