http://www.mbclub.co.uk/forums/parts-maintenance-servicing/149239-w220-night-light-illumination-lamp-interior-door-handle.html

http://www.mbca.org/forum/2011-06-15/w220-how-remove-interior-door-panels-and-how-replace-interior-handle-led-modules

The part number for the right side A 220 820 04 21; the left is A 220 820 03 21 (and it has a large "L" above the bar code on its label, and another on the gray LED support).  The right one has "R"s.