G'day folks,
As BB has mentioned, there is currently a FleaBay Oz seller offering 3D printed plastic repro gears, which use a modified original centre bush.
These are made on demand. From the seller's feedback, he's been selling them for a few months.

A FleaBay search on 'diplomat drive gear' will find them.

Dunno how close a match they are dimensionally, though - the gear tooth form looks quite different to the used original part.

Also, I'd be asking the seller which type of plastic filament is used to make these. ABS or Nylon should work quite well.
A concise rundown on the filament types currently available: https://www.tomsguide.com/us/3d-printing-materials,news-24392.html

Cheers,
Gadge

"ODK Mods can explain it to you, but they can't understand it for you..."

"Crazy can be medicated, ignorance can be educated - but there is no cure for stupid..."