Have a hunt for the battery optimiser plug and socket sets... they come with sleves for covering when not in use...
Otherwise the connectors used for cars...
erm...
hold on...
ah...
here we are...
Click to view attachmentThe black connector is the waterproof one, the white connectors are the battery optimiser style connectors.
As for where to get them and what they are called... no idea... but they sell them in Halfords and other no-so-good chav add-on car places!
The only info I can find is that they are 18AWG, connector 2 conductor (USA site)
Sorry if it's no help, but you know what I am Like Chilli!

*EDIT*

There's another piccie