I'll have to dig on out and photo, but I repaired some lamp clusters for my old convertible, I bought some cheap new universal tail lamps, bit like mini round lamps, and used the holders. I used some fibreglass PCB to mount the holder and cover any gaps.
I also used clear silicone sealer to make gaskets up, put a good thick bead on, then fitted the covers losely until it set, then tightened down, same for the cluster to body seal.