BMW's have expensive parts,. You could call around, but, I would say if you need particular part, your just going to have to pay for it.
Everything European will cost more than domestics, if you want cheap try a wrecking yard, but they are used so the life will be shorter.
How long have you owned this car? And, the mileage on the vehicle? You could be starting to enter the really expensive phase of ownership? BMW's are good cars, but, they require more maintenance than most Asian models. European cars, including Mercedes Benz, don't seem to age as gracefully as a lot of cars, especially Lexus, Toyota, Subaru and Honda. I'm not saying it isn't worth it, but, generally it's going to cost more. Unless you have deep pockets have the capacity to do the work yourself, most cannot, you might consider an alternative vehicle at some point. It's never too late to realize that you are over your head.
Unfortunately, BMW 5 series don't have the greatest reputation compared to the BMW 3 series.
What it is is that I've owned the car for about 3 months, it now has a little over 74000 miles on it. The car has actually been good to me, I've drove it back and forth almost everyday from Brooklyn to New Jersey. The problem is I let my lady drive it and she got into an accident. Which is why I'm now looking for the parts. My mechanic said it definitely can be done with no problem.
Shawn, I use fcpeuro.com for all my parts, lifetime warranty and fast shipping.
Looking for a Used 5 Series in your area?
CarGurus has 15,988 nationwide 5 Series listings starting at $1,700.
Search BMW 5 Series Questions
BMW 5 Series Experts