There is a yard in Boring, Oregon called German Auto Salvage that may have more Benz parts than most places. I have not made it out there yet unfortunately. Here's the info:
www.germanautosalvage.com 503-663-3006
I just found that Halsey Automotive has reasonable prices for new parts. I got a front wheel bearing kit there for $25 for a 1980 300D - The cheapest I found even after shopping around on the internet. I generally buy from fastlane to support this site, but I will be heading to Halsey Auto when I need the part right away.
If you find out anything about German Auto Salvage, please post. I have been meaning to stop by but haven't had the time.
Sean