The gears are available! Buy them on Tindie here.

With the sale, I can partly finance my hobby: inventing and publishing it. The further development of my Maxun One solar bike is expensive, many parts are unique and are manufactured by companies to my specifications.

See the article here.

The nylon gear is a weak part of the Yamaha PW-X / PW-X2 motor. When the motor is broken, it will just be exchanged by Yamaha. Outside the warranty period, this will cost around $750. This is a big problem because, when the gear will be overloaded again, you can keep going this way.
I cannot have the gears injection molded because the numbers are too small, which unfortunately makes production expensive.

Replacement

Remove the broken gear and glue the new one in place. Use common one or two component PU polyurethane adhesive. PU glue has been tested in practice and is very durable. Here polyurethane glue from Bison, note that the text may differ per country, as long as it is polyurethane then it is fine.