I have seen on here that you can remove the magnetic part of the pulley so the visual check will still pass. It's an older post (page 2-4). I do not require emissions test here so the previous owner of my 95 E320 removed it completely. Make sure you get the right size belt or you will have belt squealing like I do.
A hard lesson I learned ... DO NOT PUT ANYTHING ON THE BELT TO TRY TO STOP THE SQUEALING! my pulleys were all kinds of gummed up and it took hours to clean them.