Good used parts yard in Falmouth, KY of all places
 

There is an excellent source of used Mercedes parts at a "recycle yard" here in Ky called European Connection. The phone # is 800-395-8636 - tell them Holt in Ashland recommended them.
I was able to get some obscure interior trim pieces and a used auxillary water pump which I was not able to get from Potomac.

Second that... I purchased all (and I mean ALL) parts for my 5 spd conversion from them, over the phone. Bernard and crew sent stuff I didn't know I needed (even the console wood around the shifter was different). Plus the little "trinkets" that are usually left in the mud (shift linkage clips). Would do business with them again in a heartbeat.