wow. that should definitely not fly off. have you ever removed it? if not, i would definitely bring it into the dealership. maaaaybe they might be able to do something for you. i doubt it, but its worth a try. in any case, here is the part you need:
2015 Nissan 370Z Coupe OEM Parts - HANLEES HILLTOP NISSAN
its $300 USD for one.