Thanks Aaron.
Found this rechargeable Petzl, looks OK:
http://www.petzl.com/en/pro/headlamp...dlamps/pixa-3r
It takes 3 hours from the mains to recharge.
I was curious about the Minewt as it's 175grams and USB rechargeable...except it takes 4.5 hours from the mains to recharge.
Electrics are not my forte but I imagine that dynamo usb charging would take ages for both if it's possible....can anyone enlighten me?