Although the tops are not separably purchasable, they can be removed and replaced. I replaced several switch caps on my '85 300D using junkyard units. Note that most older W126 switches interchange with W123 but W124 are different. If you don't have access to a junkyard, put a "wanted" notice in the parts section of the forum.

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"Buster" in the '95

Our all-Diesel family
1996 E300D (W210) . .338,000 miles Wife's car
2005 E320 CDI . . 113,000 miles My car
Santa Rosa population 176,762 (2022)
Total. . . . . . . . . . . . 627,762
"Oh lord won't you buy me a Mercedes Benz."
-- Janis Joplin, October 1, 1970