Hi there,
It's a 3D painted part and you could use 3D printable plastic that is sturdy enough.
Use this file to print the parts:
This is a model for a top or bottom fender extension for the Stromer Speed Pedelecs ST3 and ST5. It extends de fender about 17cm (6.2 inches) at the top of the fender. The extender has the same mounting pins as the original Stromer fender endpiece but instead of springs to hold the fender in...
cults3d.com
3D printers are readily accessible at most universities and local companies.