AGCO still sells the gaskets, but you could make one out of any very think gasket material. The original is very thin. I heard of a guy that cut his out of a cerial box.
I've only change one. I got the pump in place and then worked the gasket in and around all the cam rollers, but doing it that way you can't put and sealer on so mine still leaks a little. It's really hard to get the gasket and pump worked into place without teariung the gasket.