If they are anything like the AD setup, a regular black strip with good barriers will do. The electronic shops sell them and I think the trcuk suppliers do too. Antique Electronic Supply would have them.
Well, you have three now, one for low beam, one for high and one for parking lights. So, if you want to be able to join cables for the turn signals, you will need two more terminals. Adding the one with three would give you a spare terminal.