I've been using these 3D-printed mounts made of plastic, but find the tabs wear out pretty fast, allowing the light to fall off in rough terrain:
https://www.shapeways.com/product/FF863PVAP/rotated-gopro-triple-mount
Does anyone make an identical product made of metal? Note that this mount is rotated 90 degrees from a standard GoPro-style mount so the light points forward when mounted under the handlebar.