I designed this spool for my Olivetti Lettera 32 typewriter by measuring the typewriter. I didn't have an old spool to work with. It came out great. Going to add a ribbon soon, and use an inkpad to ink the ribbon.
I don't know if it will work on other typewriters. If you tell me the dimensions of your typewriter, I'll design a spool for you if I have the time.
I printed this using a Replicator 2 using PLA. Normal quality with supports and rafts.
I printed it upright, almost like an upright wheel. Not flat.
Takes about an hour.
The supports in the middle are a bit tricky to remove, but it's worth it.