I bought a 2017 453 and the previous owner removed the Tac and whatever is behind and separate from it against the windshield.
Question: what the heck is that back piece that's about a foot long, flat and has an electrical connection??
Welcome!!! I'm sure we'll need a picture to confirm, but that sounds a lot like the windshield computer thing used for cars that were in Car2Go service. If so, there's nothing to replace. That device was removed when the car was taken out of rental service.