seeking source for individual rubber body plugs

I just spent an hour in the interweb with no luck. I'm looking for some specific individual rubber body plugs (not plastic). The spare tire well in my 70 Dart has two big body holes (2-1/2 inches). The originals were soft rubber (not a plastic caplug). This is a bucket seat car and the holes in the floor for bench seats have soft rubber plugs in them (2 have survived) these are about 5/8 inch holes. I'm looking for a place where I can buy these rubber plugs by size. Buying a body plug kit supposedly for my car was a bust.