Used this a few times but no longer have a bike. Light and battery pack work great.

Magicshine Monteer 3500S Nebula Mountain Bike Light, 3500 lumens max Actual Output, 1800 Lumen Flood,1400 Lumen spot, 5200 mAh USB Rechargeable Battery Pack, IPX5 Water Resistent MTB Helmet Light

Also includes:

Magicshine MJ-6276 Head/Helmet Mount Kit for Garmin/GoPro Devices, Compatible with Bike Lights, Cameras etc. Comes with Adjustable Headband for Head Mounting and Rigid Straps for Helmet Mounting