I found a coupe in better shape that the one I'm driving in one of the semi-local yards due to the clunker program.
It ticked me off to no end that most of the parts I'd love to have grabbed were useless due to the program, too.

Regarding the original question, I had to go looking for a bit.
I don't know of any 'proper' replacement seals for these lights, but you might look at 3M "strip caulk".
I'd seen this product originally when I had a Subaru and someone did a tutorial on how to modify the light assemblies, and used this product to replace sealant lost in the process.

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-Josh
Testing the cheap Mercedes axiom, one bolt at a time...