Well try these pre-wired 2 pin plug and sockets! The connectors themselves are tiny with the pins only 2mm apart. They are also keyed so they will only plug in one way round. Also available in a 4 pin version.
4 pin micro plug and socket (pre-wired) 5 pack (compatible with Hornby X6113)
DCC Concepts AED-SSC.3 AE Model 2-Wire Micro Plug & Play Stay-Alive 3 pk - POD
AE Model 2-Wire Micro Plug & Play Stay-Alive (3-Pack)
DCC Concepts AED-SSC.1 AE Model 2-Wire Micro Plug & Play Stay-Alive Split 3 Pack