In searching for this issue I only found a very old thread which offered no solution to the ridiculous PLASTIC ball sockets used in a bunch of Benzes.

In my case an '87 300D.

The stealership won't sell the sockets themselves.
They'll soak you for $46 for the sockets and the threaded rod.
THAT PN: 1100701675.

After an hour or so of digging, I found this PN: W0133-1901256.
Auto Parts Warehouse (among others) had them for $7.95 each.

Metal too.

When they arrived, I realized the original rod had not only damaged threads, but one end is left-hand threaded (so you can adjust the length I guess). My new sockets were BOTH right-hand threaded.

I bought two 5mm bolts and lock nuts and welded them together.
It works and is the same length as the original.

FWIW

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Albany, NY Suburbs
'87 300D