You're talking about the piece that actually holds the glass? I don't know what it's called. I would probably just bring the old one to a junk yard and see if they have one. Eurasian Motors in denver seems to have a good amount of MB stuff:

http://www.daplus.us/showmap.aspx?businessname=Eurasian+Motors&address=1394+S+Acoma+St&city=Denver&state=CO&zip=80223&Partner=appleyp