If you remove the headlight, you should see an aluminium plate sitting below the speedo which has a row of plastic connectors mounted to it. The two pin connector furthest to the left hand side (looking rearwards from the front of the bike) containing a yellow wire and a green/white wire, are the two wires which operate the front brake light switch.
If you want to make up a lead using a connector that will plug into this socket, PM me your e mail address and I'll send you a PDF showing the KTM part numbers required.