350SDL Belly Pans

I recently purchased a 1991 350SDL in pristine condition.. all except for the two missing plastic belly pans that should be mounted under the car's engine. I checked with a dealer and they wanted over $700 (!!!) for these two pieces of plastic with some acoustic material bonded to one side. Are these available anywhere else at a more favorable price? The engine clatters loudly at idle (yet V-8-quiet when throttled) and I don't like waking the neighbors for my early morning departures. These belly-pans, I'm told, will quiet it substantially.
Thanks, Dennis