Well, we found out what GM uses for window regulator cables.
They are called a BOWDEN Cable.
You can read about them here:
They cost about $3.99 each pre-made at any bicycle shop. The thinnest ones
are 1.5 mm and that is what is used in our electric window mechanisms.
The motor is a capstan winch with two of these cables on the same capstan.
If you can tune a fishing reel then you can fix this.
Save big bucks!!
You may need to shorten a cable so buy some 1/16th inch end ferrules and a
crimper or press tool. You will pay about a dime each (tops) for the
ferrules - but they may try to whack you on the press. I made one from a
steel expansion plug that fit into the jaws of a bird-beak vice-grip.