I bought a lot of 4 speed knobs (10) from the states as I couldn't find a decent 5 speed , I manage to find a really nice 5 speed button to make a mould from, thanks to another member in Brisbane.
Injection moulding would be the way to go as making them one by one was a slow process, and trying to get rid of all the air bubbles was my greatest challenge .
I don't go home as much as I would like , and I miss my zeds as I have 3 sitting in the shed.
Happy to pass on my notes if anyone wishs to make their own.