With a drilling machine you can cut such small pieces from a woodden plate. Drill another hole in the disk an cut a small stripe from this hole to the outer side of the disk. Put a small stripe of a copper ribbon around the wodden disk and put t both ends inside the second hole. You can fix them with another piece of wood. At least you solder them together. Next sign the holes you want to drill for the brass srews and for cutting the inner circle to put the plastic bulb later in.