I don't do this sort of work on RVs, but I did it a lot on boats. Even if you can buy the part, shipping it will kill you because of the size. If it is actually fiberglass, or any plastic that epoxy will bond to, repairing it will not be all that difficult or expensive.
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.