In the panel next to the hazard switch is where I put mine.
If you don't want to drill panels you'd need to talk to Bill McAvan at BLM Accesories. This is the guy that makes light brackets and aux. fuel cells. Not cheap, but some nice stuff!
I stuck mine on the left switch housing, just under the windshield retract switch. That way it is an easy thumb reach and I don't have to "look" for it. IIRC, I used some silicone sealer as that isn't a "flat spot" to mount to.
I shamelessly stole this location from Tinker after seeing his bike.
And more than welcome Mike. I used velcro rather than silicone. Still trying to work the switch into the left housing. Not a whole lot of space to work with.