Please help! Trying to source a trunk drain plug.

I've been looking all over, calling parts stores, and can't seem to find a re-pop or OEM rubber drain plug for the trunk floor of my '67 Belvedere II which is missing. It's one of the large ones up above and toward the front end. I measured one of the intact ones and It measures about 2 1/4" across the rubber. I can't find a part# anywhere either.
Sure appreciate some guidance on this. The duct tape someone placed over the hole a loooong time ago...ain't cutting it!
Thanks. :)
Author: BLUE DOBB