Here is my post on this from a while back...I just got mine from a local dealer because nothing came up online at my normal vendors:

http://www.benzworld.org/forums/w124-e-ce-d-td-class/1506544-rear-sway-bar-bushing-part-number.html

And in short, here is the part number:
124 326 05 81

__________________
1987 300TDT - 195,000 (Original #14 head)
1993 190E 2.3 - 105,000
1981 300D - 250,000