Hi, W. You should be in luck. From your address, you should have plenty of fiberglass boat stores and repair facilities near you. Hang around a couple and see who does good work and color matching. Repairing a fiberglass boat hull with scratches and repairing your shower are really the same thing.
The appropriate cash deal with the local expert is probably your best bet. It will certainly be a lot cheaper and easier than replacing the shower even if a new shower stall would cost less.