Here in Az we can register them for on road use. When I mounted ours I just got a small piece of flat stock steel and drilled 2 holes through it and bolted it to the frame under the back tool box. I then bought a liscence plate light for a motorcycle for about 7 bucks and screwed the plate to the light. It looks good and serves the purpose well.

 

I know that some of the countys in Idaho have ok'd use on county roads.