Steve the photo of the lathe reminds me of one I bought in an excess equipment auction from a school system. I the part mname painted in white letters on the headstock, tailstock, ways, etc.
Rubes,
If you live near a small city it will most likely have a machinery company that may be able to fix you up. If the lathe you have has machined ways then any banjo of the correct height will probably work. The banjo sits flat on the ways and the only sized part you would need is the locking plate that is usually round stepped disk that fits into the ways. You may be able to use the one from your old banjo.
Its been a while but I took a broken banjo into the Skarie Machinery company in baltimore. The actully had one in stock that fit. They could also order most anything.
happy turning,
AL