I haven't found any discussion of this ... Most all of my clearance lights are broken/missing/or missing parts.. These were Auto Lamp 661, I see that vintage trailer supply has the plastic lenses, and there are some complete lights with glass lenses currently on ebay and it looks like I can find new bulb sockets, but I haven't found: 1) A source or substitute for the metal retaining ring? 2) Or a possible replacement that uses the same 2 mounting holes (4 inches on center, vertically) I would like to avoid filling a hole for each one.
You could look on ebay, tho I'm guessing you will have to buy the whole light. I'll look and see if I have any old lights but doubt it. The base and rings are hard to come by. Another source may be firstname.lastname@example.org.