I have a good one available that was removed from an '88 635csi, I'm pretty sure it's the same unit, plug and play. Someone will correct me if I'm wrong.
Send me a PM if your interested.
1986 328is (M20 Stroker)
1986 535i (5sp all original)
1990 325iX (Mint 5sp all original)
1989 325iX (Winter auto X car
2001 740i (Supercharged)
2004 X5 3.0i (The DD)