'98 C280 with rattling noise in exhaust

[clankford]

I have a 1998 C280 MB that has a LOUD rattling noise near the center bottom of car when idling at low RPMs. I have narrowed it down to the exhaust system. I have what appears to be two small catalytic convertors where the exhaust comes off the two header pipes. The noise seems to be in one or both of the convertors. I can rap on them with my hand and "near duplicate" the rattle. The rattle almost sounds like a loose hanger bracket, but all of the mounting assemblies are very secure. The catalytic assembly appears to be bolt-on with welded pipes fore and aft. I noticed that FastLane appears to not carry any of the exhaust system parts. Is this something I can only get from MB? I would like to keep her 100% original, but I feel this is going to cost me an arm and a leg, even with ME doing the labor.

Any thoughts on the least expensive way out of this?

Thanks again, guys!

Curt