Lewmar Gaskets
I had the same problem. I called Svendsen's in Alameda,CA. They are the West Coast parts distributor for Lewmar. They are also really pleasand to deal with. They figured out what model port I had in about 1.5 minutes and then just asked me how many I wanted. Their price was significantly lower than list and anywhere else, and they ship fast by UPS. Make certain that you clean the grooves well, use marine silicon adhesive, and follow the directions. Lewmar is Brit. Thus the diagrams and directions are counter-intuitive for North Americans. Do a dry install first.