Endura 8w with loose end cap

This Endura was from another 70s new old stock 12v caravan type fitting though this one does have a better quality inverter that pre-heats a little on starting. When I removed it the cap came straight off! I have managed to re-solder the connection wires but was wondering if anyone has had any luck with glue. Most claim to be able to glue glass and metal but in reality are only any good at sticking your fingers either together or to something else, which I've never found to be useful! Any good recomendations appreciated.