None of the parts you mention are specific to the E24, e.g. rear window motors are the same as the e30, you can get alternators new for the E24 , my mechanic just got one for mine easily, starter motor I'd rewinmd the one you have, cheap just done that on my Lotus.
In Malaysia everyone asks you 'what car is it for' don't answer that question, they all tell you they have no bits for an E24, look at part numbers.
I have a Sylva, which is the only one in Asia and they all say no parts, but it has a Nissan Motor and Ford Suspension so I've learned to just ignore them and give them part numbers,