So I have both mountings in hand.
LH mounting is as listed above A4602421013
RH mounting received is A4602420813, which seems to have superseded A4602420513
So it's confirmed:
1. That Mercedes still supplies these mountings
2. That although the mountings look similar, there are different part numbers left and right. I assume they have different rubber composition, either because of the torsional stresses caused by engine torque, or because the RH mounting sits next to the exhaust.