Unfortunately with the advent of serpentine belts the changing of compressor brands has become near impossible. They are just too specifically mounted.
When the only answer was a POS rebuilt or a new MB for a grand we used to use Toyota and Acura 10P15C and 10P17C Nippondensos for about half the price. MB list on their rebuilts without clutch now is $443 for all of the early Nippondensos. The only improvement might come from using a 10PA17C later 300E compressor on the early cars. I have never tried it but you would have to change the clutch and manifold assy and mounting bracket I imagine and you might wind up with a necessary belt size that doesn't exist as there may be other pulleys that changed too.
We don't do early 300E retrofits if we can avoid it as the early 15C compressors are under powered to start with. I think the 210 chassis has a variable displacement compressor but I bet its capable of 20 or greater by whatever measurement that represents.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician