Interesting choice to fix this super common problem! I also have a (facelift) W140 with the 3-piece bar in back, and it had the same issues as yours.... I decided to wholesale replace ALL the components with new ones. The L & R lamps were available from ULO (oem), and the Center section was a Genuine mercedes part (wasn't NLA a few years ago). The result is just as stunning and beautiful as you would expect! Although it did cost me between $6-700 in total! Also, genuine Mercedes parts constantly are going "NLA" and then comping back for a production run all the time. You really just have to keep checking periodically to see if they are available!~
