Everything I've heard on 126 is that they're "single use". So you wouldn't find a used one. I need one in probably the next year for my SD, but fortunately not for a while on the SEC. Maybe MB will do a run of them.
Not sure what part you are referring to. if its 126-670-02-39 that part is available.
For almost any part I order I check this website first to see if MB has it anywhere. If a dealer says they cant get it, then they're BS. call classic center then.
All the MB dealer sites and a lot of the other use generic parts databases, so it always shows up as orderable. And they are right, it is orderable, its just not deliverable......
Mercedes-Benz Classic Ersatzteile
BTW you have to put an "A" in front of any regular part number and an "N" for hardware. no spaces or dashes.