When I was messing with my sockets a couple days ago, one of them was so rusty that I felt I couldn't do an adequate job cleaning it up while it was all assembled, so I started pushing and pulling the socket apart. I think I was even able to push the metal tube portion up out of the plastic holder. Point is, I think you might be able to reuse your original plastic housing portion and just replace the metal interior section with a new one. That might be another option if we can't find a suitable mechanical replacement? Same fit into the tail lamp housing as before, but new metal where the bulb inserts?