We replaced the freshwater pump on our Westerbeke W70 with a Misubishi
truck water pump -- our mechanic in Trinidad just happened to know
that's where Westerbeke (which doesn't make its own engines, but
out-sources every single part) got their pumps. You can try posting
your question at http://forums.torresen.com/.

You don't want to replace the seals. They're designed to fail when
the pump itself starts to fail. Replace the pump.