I have been looking for years to replace the rubber flaps covering the cockpit transom drains. I think Post used these during the 70's and 80's. I finally found it here:
http://www.mcmaster.com/nav/enter.as...2&pagenum=3447
The 12x12" piece works perfectly to make both of them. Part # 8143K14. The white color is actually offwhite and matches the gelcoat well.
Hope this helps anyone looking.