Kisan Signal Minder is the way to go. If you forget to use your thumb it works great! The T/S module is accessed through the little door on the front of the fairing. You have to pull of the windscreen and the mounting frame to get to it.

The Kisan ties into the break light module so when you brake the thing doesn't turn off. It also gives you running lights (for the front and rear) and 4-way flashers, for those who use the flasher switch for something else.