Is there a commercial shoe isolator that will provide the center
terminal only for connection? Or do I have to build one?

A well-stocked photo store should have one. The shoe and central terminal
connect to a short lead with a PC connector. (I bought one a few years ago.)

I'd recommend covering the bottom of the shoe with two or three layers of
Magic Mending Tape, then cutting out the area over the central terminal. The
tape keeps the extra pins from contacting anything.

Afraid of the glue goo.
Maybe some thin polycarbonate.

I'll look for that shoe, I think I actuall hd one at one time so it is
probably in the camera cabinet.
But my flash does not have the standard PC connector I think.
It is a unique Nikon connector.
I have a cable for it but I hate to cut it up to use it.

Thanks for the input.