It's called, variously, a BMW, DIN or Powerlets socket. And it should be fused - as a standard fitting on the latest Sport.
You can buy various conversion cables on the internet (though probably a TomTom supplier the best source) to power your TomTom. But TBH, I think you'd be better off leaving it free so you can, for e.g., use it to charge your mobile phone or something. TomTom should have supplied a pukka connector loom to wire into the bike - I'd use that - there is another connection point under the tank. Or you could even use the USB port under the seat.