Al,
This chap has provided me many oddball OEM parts over the last two years - and I've never been disappointed - he has good listings, and seems to be a straight shooter. See via
http://cgi.ebay.com/Mercedes-Hood-Star-250S-250SE-280S-280SE-280SEL_W0QQitemZ7917314572QQcategoryZ33643QQcmdZViewItem
If you visit his store, you'll see several offered, plus lots of other goodies. He specializes in buying old stock from closing repair shops, sell-offs, etc - have seen everything from simple knobs to a new 600 Grosser heater unit...
Yes, he's listing a 280SEL 4.5 for $60 (other models are less than half as much) Buy It Now, but also frequently sells via Make an Offer - email him via the eBay link, and see if he'll do much better - if not, someone else may well do so.
Used often have corrosion at the joint(s), exactly where yours failed...
Stan