Another crazy little piece needed for 70 Swinger.

I bought a pair of mirrors for my car and both have no remote adjustment. Now what I have is a nice hole in the upper side of the drivers door where the remote mirror adjustment knob was. I have seen cars with a plug in this hole. Does anyone have a spare one or perhaps know where I can pick one up. I was thinking this plug is pretty close to the size of the handlebar plugs on 10 speed bikes with the drop racing handlebars??? Thanks.
Chas.