As others have pointed out, you appear to have a UG & HG compatible freehub. You have three choices, old school UG, modern HG or even a hybrid of the two.

The good news is that if you can't find the UG spacers, modern HG SRAM, Shimano, Sunrace, etc, can all work on that specific hub. If you plan to shift in friction mode, they don't even care if you run 9 speed spacers and add an extra sprocket to move from 7 to 8 speeds. Your key is to purchase HG cassettes which disassemble with either a long screw through all the sprockets or a rivet which can be ground off. Then go to town being creative with the specific gearing you desire.