Thanks! I need to do this on a few of mine.
Since I was looking up the part numbers, here is what I found, figured it might help someone else.
Confirmed for W123 sedans, may work on others:
Protective boot for Front doors up to end of model year 1982 - 1078210097
Protective boot for Front doors starting in model year 1983 - 1268210397 (about $17/ea
)
Protective boot for rear doors, all model years - 1238210697 (about $4/ea
)