That arm is a hard item to find, just by itself, unless you stumble onto a wrecked wagon somewhere. Maybe a post in the Parts section would be fruitful. I'll keep my eyes open for one too
I do have a rebuild kit in case you need one

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'95 E320 Wagon my favorite road car. '99 E300D wolf in sheeps body, '87 300D Sportline suspension, '79 300TD w/ 617.952 engine at 367,750 and counting!