That's called Knock On Edge Trim.... Try J&J Auto Fabrics in Rialto, CA, they ship anywhere, good people.... here's a link:
Automotive-Marine Vinyl and Upholstery Supply
Look on the home page at item RS-439 . That material/shape is available in a range of sizes with the "Bulb" on either the side or front edge. If you send Joe a sample of what you have, he will will send you a sample of what he has that best matches. Be sure to tell him how thick the fiberglass is. It's what I used, works great.