Needed, floor mounted drain plug

First off, forgive me if this has been posted before. After an extensive search, I came up dry.

I have a 1963 Grummon runabout with the floor mounted drain. After looking for several hours can't seem to find a vendor for a plug. It's the one that threads into what looks to be pipe threads but isn't and is about the size of your finger. Has a tab on the top to turn it and has a rubber washer to seal it. I can usually find anything for a boat, (30 years in the biz) but I can't find one anywhere. Any help would be great.

Hope you find one as I will need one also. If I find them will let you know.

Your timing is just a little bit off as I scrapped a boat with one of these plugs in it this summer. If I had known they were that hard to find I would have removed and saved the plug.