I believe the clips which hold on the trim is actually a body assembly part, so I'm thinking you could take one to a body shop and they could match it up. They remind me of the clips used in years past to hold on windshield trim in GM cars.
Basil, take a picture of the trim piece, and again, a body shop should be able to help you. If not, then check out this link, and give the lady a call, she most likely has some of the trim in her stock.
Northwest RV Supply