Peter, when the part number prefix is the same as your model of machine,(CS19R) Then it means Ford never had that part in their system until they built that particular machine. It may have then been used in later Fords, but I suspect it is special to just a few war time machines.
If you have some made, some originals may then materialize. That seems to be how it works.
Another angle is to check out the various parts lists from the different suspension seat makers like Bostrom etc. Some have scissors that may have the type of bolts you are looking for.