Plastic parts are pretty hard to find for our older trailers. You might find used stuff but it will probably be cracked, too. If you want a new shower pan you will probably have to find something generic. I think the best way is just to fix your old pan if its fiberglass. Scuff it up, piece it together, glass it like a sandwich and paint it. Go to someplace like US Composites for materials and info. If its ABS or other plastic you probably won't be able to fix it but you can use it as a guide. Make a plywood copy and glass & paint it. Take the pieces to an HVAC shop and have them bend you up some stainless. Chances are when you get all done you will find exactlywhat you want but too late.