Bummer,I lost the exact same one on the other side when pulling fuses last week. Somebody here a few years ago had an ATV site that carried them cheap but I can't remember the site or member who posted.
Update: found the ones for the smaller size (8mm) ? For the windscreen. I wonder if the 10mm option would suffice. Tusk Replacement Fender Rivets | ATV | Rocky Mountain ATV/MC