I've disassembled my taillights. The light sockets on both sides had a black flexible o-ring between the socket flange and housing. One of them was broken that I need to replace, assuming this is necessary which I'm guessing it is. The o-ring looks like it could have been made by liquid gasket material.
First picture is the top, second bottom against socket flange.
Is the o- ring needed and if so where can I get them or how can I make one?