A little more googling found other sources for the cord referenced in my first post, in stock, at a better but still high price.
But the comment by coromonadalix set me on the road to the solution I am going with. The cords shown in the first picture (sorry about the quality) are available for a couple of bucks and fit the pin spacing. That plus the adapter shown in the second picture, printed in TPU, and some gorilla glue or epoxy will give me what I am looking for. It turned out the the pins are a bit off center in the aperture, which is unusual I think. A am attaching the FreeCAD model of the adapter so that others can modify it to fit their needs.
Finally, and just for fun, a picture of the radio in question. While I haven't got an exact date for it, it is one of the last in the AA5 line, uses miniature tubes and a PWB for connections. Wasn't new enough for the electrolytic power supply capacitor to be good, but dug the innards out and replaced them with modern units that fit easily in the old case. Looks original. Now working reasonably well, but still need to align the IFs.
Thanks again for the help and suggestions.