The Nightster side mount set-up is pretty easily adapted to just about any bike. It isn't chrome, and it isn't cheap, but if you can get a take-off from someone wanting to add saddle bags, you can get it cheap. The bracket is aluminum and can be cut and filed easily. Since it mounts to the fender struts and not to the axle or swingarm, it will probably last far longer than brackets mounte to those moving parts. Also, it has LED illumination for the plate, meaning almost no current draw. And the circuit board is designed so that it is not polarity sensitive making it easy to wire.

I'm setting up my Sloptail with one I got for free. I like free.

 

Oh man.
You are talking about my favorite price.