I have for sale a passenger side mirror boot for any W124 model. This boot is an 8 out of 10, and came off of a 1987 W124 car. It is, as you can see from the photos, still quite flexible and pliable, though perhaps 80% as flexible as a new unit, hence the discounted price.
However, it is a GREAT unit and I put it in VG+ condition. None of the loops are broken. If I were looking for a replacement, I would not hesitate to put this boot on my car.
$55 shipped via US Priority Mail.