Here are pics of mine before disassembly. Again, it has been so long, but I think they broke during removal. I should have been more careful. I am sure I have these tagged and bagged somewhere.
Yes I concur. 39mmx19mm. FYI, Original does not look like the black one you have. I will try to find one of my originals to post, but they are long NLA. So something is better than nothing. But basically it was a flat gray plastic deal.
Matt, have you ever tried to see if this oval plug is same size as the two oval openings on the LV doors? In case your not familiar, LV doors have oval openings for window frame bolt access.