I see you've just joined our merry little band...Welcome aboard!
First a little history: Mansfield Plumbing introduced the VacuFlush (which is what you have) in 1978. Mansfield spun off their marine toilet division to SeaLand Technology in 1984, and your toilet became the SeaLand VacuFlush. Dometic, a European company specializing primarily in RV prodcts, bought SeaLand Technlogy 8-10 years ago and continues to make VacuFlush toilets...which have changed so little except cosmetically since Mansfield introduced it that the same troubleshooting guide still works for all years, all models/versions.
So yes, you can still get parts, but they're only available from "authorized VF service centers" and Dometic is VERY proud of them, pricing 'em accordingly. So depending on what you need--which is hard to say because it's VERY unlikely that anything in yours is still original...the only question is how much is relatively new--it may make more sense to replace it with a top quality macerating electric toilet.
I've written a piece I call "VacuFlush 101" that explains how it works and how to maintain it...I'll be glad to send it to you along with the troubleshooting shooting guide if you send me a PM (private message) that includes your email address (no way to attach anything to a PM).
--Peggie