Hi Paul. Are they the big bazooka type lights that stick out the back? I had trouble with those lamp holders always coming loose. I got shot of them in the end, see this old
post. If they are “I think” those Morgan hybrid lights might use screw fitting lamp holders from military LR’s type
Lucas 576207. I don’t know for sure as I never did ever buy replacements for mine after the mod.
Good luck tracking them down.