Hi I would first check the model number. It should be on the base of the toilet possibly behind a base cover. Mine is also listed on the coach build sheet. I have a 510 plus and replaced all the operating parts with a screwdriver (the $2.00 variety from harbor freight that has interchangeable bits) From what I can see, Sealand/Dometic and didn't really change much of the working parts on their stuff so I have a hard time with parts being unavailable, but you really need to be sure about the model number first.
Best