I have made a few successful light mounting bracket out of upcycled chainrings. They work quite well for something that would normally be thrown out or recycled. The upside is that they come pre-drilled, are easily cut to size, easily cleaned up with files, sufficiently rigid to support most lights and are relatively light weight.
I have a similar solution that I have used with battery mounted lights as well.
This one has served me well, but as I get ready to switch this bike over to a dynamo lighting system, I thought is was a good time to share the set up. There is a lot that the home hobbiest can do solve challenges like this with basic hand tools and a trip to the local hardware store.
Here is a sneak peak of the mount I am working on for the upcoming dyno system. First step is tacking and filling with epoxy. Next up is a composite wrap. Conventional wisdom is that something like this needs to be brazed. If whole bikes can be built with bonded metal and composite systems, I am sure light mounts can be done just fine.
Next steps are to smooth the filler, clean it up and wrap it with a resin fiberglass matrix. More on that soon.