I was asking the same question a few years ago. I had wondered if it was possible to fit an older euro model 500C switch to the Ascot as the euro model had a light switch. At least, the euro repair manual shows a light switch but I was never able to confirm if production models had a light switch or not. In any case, I seem to recall the research I did suggested the right hand switch would not fit, or perhaps more accurately, it wasn't plug-n-play. Doesn't mean you couldn't splice one in.
As I recall the Ascot's switch harness' plug into the junction box under the headlight. Do the C models have the 'junction box?