Get a cheap parts car!
Ebay.de is your friend lol for your euro needs lol
Like Max said, r3vlimited.com is good. E30tech.com is another one.
There are a few e30 part hoarders here on Max! E30 tony is a good person to know! If he doesn't have it I'm sure he can find it.
Also PJ from bimmerboys has been nothing but great to me. I have done a good amount of transactions with him.
I know you guys had a hiccup along the road, but he can get brand new stuff for extremely reasonable prices. He can even source used stuff too.
Anyways, hope this helps and I love your 5er lol