Ignore the housing, the insert looks the same as every other dome light of the 60's and 70's and the rest, just have to find one that has the removable insert, not cast as part of the housing.
Having said that, more and more these days are part of the same casting and simply have the terminals mounts masked off when chromed. But they do still exist.
Here's the same idea I was talking about but a reproduction of the GM parts in Australia.
https://www.ebay.com.au/itm/40264609...hoCIG8QAvD_BwE