Had the same problem.  I made a temporary fix by creating the missing
plastic gear teeth out of a very strong epoxy.  Just poured the epoxy
mix in the area of the missing teeth and when it was hard, cut the
epoxy teeth with a small fine saw blade.  This lasted long enough to
get the car past inspection. I eventually replaced the motor with a used
one which had a good plastic gear, but the point arm was broken meaning
that the wipers work but don't self park.

Mike

Hi Chris,

   just take the old motor to a wrecker and find something with the same
size spindle. You may need to experiment with the wiring but it isn't rocket
science. It would be good if the mounting holes matched up as well, but this
shouldn't matter too much (will just require a bit of fabrication). The
wiper motor on my Alfa 1750 GTV rusted out and I quickly replaced it with a
nearly new one out of a Toyota Hilux van for around $15. I needed to modify
the mounting holes, but the new wiper is smaller, quieter and more efficient
then the old one.

Regards,
Dominic.