Stardot forum user roland asked about printing a capacitor. This is a cover that can be slipped over a modern Vishay axial capacitor and painted to make it look like the old caps from 1940s radios. You'll need to print two and glue them together over the capacitor.
NB: I don't know if these caps get hot, expand, are a fire risk or anything. Print and use this at your own risk.