Where's the best place on 2007 C90 to find a switched wire for a handlebar mounted radio ?

 

found a parts drawing or service manual that showed an auxiliary plug in the headlight housing. this is a switched, auxiliary plug from the manufacturer. it had nothing connected to it but had female spades on the power source side and matching, empty plug on the "destination" side. so i was able to insert male spades into the "destination" side and plug them back together.