For sale is a used but well maintained BWM carbon fibre strut bar. This is not a knock off. I got it from BMW directly. It fits the e46 chassis (not the M3 though). It comes with bolts and 4 of 6 bolt covers.
Asking: $400 (local pickup)
Note: While putting this on the car is pretty straight forward you should know that you will need to move the positive battery terminal. For most DIY'ers it won't be a big problem but if you're more DDIY (don't do it yourself) you'll want someone else to do the work. Here are the instructions for your review.
Here's another one