Go to www.bmwusa.com, click on the Certified Pre-Owned Link, and then search to your heart's content. That is how I found my car, it took a few months (6MT 550i's are even harder to find that 135 or 335's), but I was patient, and found exactly what I wanted. Had to fly up from LA to San Francisco to pick it up, and then had a blast driving it home along the coast.
Good luck!!
Keith
Good luck!!
Keith