What kind of (1950s era) lock is this
You can try a different search phrase as "Thumb Turn Security Latch".

There is a seller on eBay that has new stock available in range of finishes. Here is a picture of the offering.



Considering the price you may just want to consider purchasing new units instead of trying to locate parts for the old ones that are broken.

The trade name for these seems to be: Deltana mortise bolt

You can find those at many web sites including at MyKnobs.com.

Here are some dimensional pictures from a Deltana specification sheet so you can compare to your existing items.