The Euro door pins are part number 123 766 00 22. I confirmed this part number both for the Euro 124.036 and the US 126.045 (560SEC). It is also used on many other US models, including the 123 and 124 US coupes. Unfortunately parts.com is not listing the part as available. So, I would talk to Tom Hanson at the Classic Center.
The circular door pin/knob bushing is part number 201 992 12 05. Cost at parts.com $2.40 each).
The US door knob is part number 110 760 05 65 (superceded to part number 110 760 05 65 9B51). Cost at parts.com $2.04 each.
Cheers from Seattle,
Gerry