You can also get GoPro mounts that sit in your headset spacer stack (I've seen a few 3D printed ones, though I don't know how strong a headset spacer needs to be for safety). If you run your bars high enough, you could probably also flip one of of these around and run the light right-side up, eliminating beam shape problems.
Planet Bike also makes a very nice, solid, fork crown mount for $10 shipped. It has a PB-specific mount, but you can remove it and it exposes a conventional round knob that will work with most handlebar mounts. I use a Dinotte XML-3 with it, though it's a bit of a tight fit since the clamp area is pretty narrow.