Had a stripped big gear on a front window regulator on a car at work. Found a good gear from the rear window of a parts car that had the same arch, and cut a piece of the gear out. Laid it over the stripped gear and scribed to the bad gear for fit. Cut it out and welded the good piece into the original gear. Worked perfectly.
And, if you ever want to convert to power windows, late 80s, early 90s Ford window riser motors mesh perfectly with old gears. Just cut off the handle and adapt the motor.