From the "I Heart O'Day's" website:
For parts that are specific to O'Day boats, the best source is Rudy Nickerson at D & R
Marine. Rudy was the materials manager for O'Day before they, like a number of
sailboat manufacturers, went bankrupt in the late 80's/early 90's. Rudy is a storehouse
of knowledge about O'Days and can most likely hook you up with the parts you need.
The website is D & R Marine
-- you might want to give Rudy a call on the phone, it
has been reported to work better than e-mail.
When I was looking to replace the opening ports in my 1981 Hunter, I was able to order them from the manufacturer, Bomar.