O'DAY 12 and Widgeon were different models, same hull, but different decks and rigs.
I suspect that wooden plug was a replacement for the original boom insert, orignal may have been aluminum or plastic. You might be better having a new part made?
Anyway, what you have is definitely an O'DAY 12, not a Widgeon. It may be that this is one reason that Rudy didn't seem to have what you need, but then I'd be surprised that he didn't suspect that you actually had an O'DAY 12, instead of a Widgeon, and asked more questions. Rudy doesn't have EVERYTHING from his store posted online, best to give him a call (508) 644-3001 he does have e-mail..... but phone call is better and he is a storehouse of info on O'DAYs.
O'DAY 12 (1977-78)
Cat-rigged (single sail) like a LASER (well ,sort-of?)
Wooden Daggerboard
Fixed rudder was standard, kick-up optional
More of a sailing dinghy/preformance boat.
Widgeon (1963-89)
Sloop-rigged (2 sails) Spinnaker optional
Fiberglass, pivoted centerboard (lever operated 1963-70, line-controlled 1971-89)
Kick-up rudder
A Great trainer/learning boat, used by many sailing schools, often viewed as a "kids boat", but as an adult, former owner of one...... the Widgeon is a great little boat for everyone!