G103 tow hook pulley replacement

Grob 103 Twin II. There are two pulleys that route the tow
release cable to the nose tow hook. We discovered that
the forward pulley, which is hidden inside of a duct for the
vent, has a sector (about 45 degrees) missing on the plastic
sheave. We believe that the sector broke out long ago
and we have been flying with a defective part.

Does anyone have experience with this pulley? Any suggestions
on replacement part suppliers besides Grob in Germany?
I have also heard that some people have replaced the plastic
sheave with an aluminum version.

Any information would be appreciated.

Thanks,
Charlie Martin
Soaring Society of Boulder