Wayne if you have an RV dealer near where you can get a catalog from them, it probably has some sizes available or "google" it and see what comes up. If you are limited to a specific size you may want to try to make your own. I put a shower in a 69 Compact but could not find anything that would fit that exact space. Check with a metal shop about making an aluminum or stainless pan and then use some type of waterproof walls. I made my pan from fiberglass wall board like you find at Lowes or Home depot. I used the corner joints to attach a 6 inch riser and glued together with marine glue. Once all was glued and dried I went back and sealed all joints with silicone. Then I let the wall board overlap on the riser to make it waterproof and sealed all joints of the walls with silicone also. I also used the fiberglass board on the ceiling. Then installed a drain in the floor.