Originally Posted by Qsilver7

I would suppose the first place would be my local BMW dealerships parts dept. Or, I could look up the 11 digit BMW part number at sites like Realoem.com or bmwfans.info...then type "BMW xx xx x xxx xxx" into a Google search box to find vendors that sell that part online.

If you can't find the 11 digit part number in the database...then look at the light on the other side. If you take the lens off or look real close at it...it should have either the whole 11 digit BMW part number or the shortened (last) 7 digit part number on the lens.

See item #4 in the diagram and part number index at this link to get the 11 digit part number for the rear lights that are located below the rear seats: RealOEM.com - Online BMW Parts Catalog. (There's an image icon on the far right of item #4...click on it to verify that's the part you're looking for)