Fitting an extra toggle switch to the dash undertray is easiest. Plenty of room internally above it to take the switch body and its easy to drill . When i fitted a klaxon, I placed the button on the section next to my right knee.

Doug
2011 Plus 4 in Rich Maroon

1972 750 “ComDom” sprinter
1958 Triton 650
1992 Triumph Trophy 900