Sure, parts car stuff should work fine. 250s and 280s had the same rear ends.

No idea on who would rebuild. You might contact Boge (manufacturer) directly:
ZF Friedrichshafen AG | Startseite | Antriebstechnik und Fahrwerktechnik, contact (tradition@zf.com ). Black Forest in WI might have another (domestic) answer: 414-228-4899. Neither would be cheap.

Used compensators pop up on ebay w some regularity, there's one up there for a couple hundred at the moment.