The mirror can be replaced separately from the whole assy and could include the broken part. There are many possibilities. We occasionally fix mirrors with pieces from other broken mirrors (having a body shop helps here). There are no other separate pieces (except some wiring harnesses are separately available).
The part number you gave has a "B" in it. There are no letters in that section of a MB part number. The "B" should probably be an "8". The device is located in the right kick panel I think.
Bosch Master, ASE Master, L1
33 years MB technician