You mean the black rear covers? I have a few different models, one looks like the eta with a removable snorkel for the air intake. The 325i and 318i share the other one, with a hose going through it IIRC. I'll check later tonight for part numbers. I tried to insert pics too, but now I host them out on Photobucket.
I'll sell you one from a 325is if the part numbers match...but after postage it'd likely be cheaper to grab one at a local pick-n-pull.