Spare part for Hobbyking 1/18 Short Course Truck transmitter

This is the steering shaft for the HK short course truck transmitter:

https://hobbyking.com/de_de/1-18-scale-4wd-rtr-short-course-truck.html

The shaft is mounted inside the transmitter and connects the steering wheel to the potentiometer. The original part breaks easily and is NOT available as spare part.