Hey CJ, I had something similar happen to my drivers side mirror. Don't know if this will apply, but you never know.
Inside the motor there is a kind of ball and socket setup. I disassembled the unit and called EVERYWHERE to see if I could find just that pert. They all laughed and told me it was a new mirror nothing and that there was no way, no how that it could be repaired. Since mine are smooth and painted white to match my car this was an unacceptable conclusion.
Well, you know what a hammerhead I am, and NO ONE tells ME I can't fix something until I prove it to myself. I tore into it and discovered that the socket part of the rotating mechanism had broke,. After giving it a good deal of thought I came up with a way to fix it. I cut a piece from a rifle shell casing (brass 30.06) and shaped it into an oval then used some JB weld to attach it and reinforce the broken area.
Well, that mirror works better than the one on the other side and vibrates less on the road and has been that way for a couple of years now.
In essence I suppose I am saying to have a look, and be creative. You never know, you may be able to save a couple hundred bucks. You may even be able to find one at a wrecking yard that has cosmetic damage that they would let go for a birdsong and then gut it.
Let us know how it goes!
Kate