I also got a German plate on Ebay (for $10.50). It already had 2 holes in it so I held it up to the bumper and drilled about a half inch into the bumper with a 3/16" bit. I then attached it with 2 long 3/16" aluminum pop-rivets. A cleaner job you couldn't ask for.
P.S. The car is a '86 230E Euro model that is FOR SALE, check the classified section.