I have looked into this issue (the jam jar rear lights).
The angle between the plastic valance and the rubber bases is the same as between the wings and the front indicator lights. So the rubber plinths for front indicators should work. Then you could use L691/692 lamp bases and lenses (red and clear).
It would be a "proper job" and all the rear lights would match. My only question is whether the rear fog would be bright enough for the OE spec, but as a mod that wouldn't matter - I hate rear fogs anyway, as they are normally misused to blind following drivers.
Nigel
