Look for good used mirrors from early 124 sedans/wagons... 1986-1989 vintage. These are the donors for good boots. However, it's a lot of work to R&R, and pray you don't tear the 35-year old boot.
I assume you don't want to pay the piper for new ones... currently ~$250/pair from discount dealers (124-811-01-61 & 124-811-04-61). Price history
here.