My Benzworld thread has some places to buy the Joint and some part numbers.

U-Joint 2005
Can you replace the universal joints????? - PeachParts Mercedes ShopForum
Tightening Drive Shaft Collar Nut 2011 post #40
How to replace the driveshaft support (carrier) bearing - A step by step guide - Page 3 - PeachParts Mercedes ShopForum
My Benz World post with all of the U-joint sources.
Another U-Joint / Driveshaft Thread - Benzworld.org - Mercedes-Benz Discussion Forum
My U-joint Repair thread 2011
Drive Shaft U-Joint Is Staked/Crimped In Place, Now What To Do? - PeachParts Mercedes ShopForum

Ther maybe more below
DIY Repair Links
http://www.peachparts.com/shopforum/forumdisplay.php?f=82

http://www.peachparts.com/Wikka/DoItYourSelf

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84 300D, 82 Volvo 244Gl Diesel