Funny you say that - I've been through about 3 sets of plugs/sockets trying to find one that would actually lock and hold tight. This last combination seems to be the best I have, yet it's still not quite right.
ARB offers a wiring loom kit with 12v locking socket, so I may give it a shot.
1976 FJ40 - green and mostly stock
1996 FZJ80 - not so stock