I know some one makes a module, but I have taken a old Servo & gut the motor out of it, extend the wires.
Plug it into a 3rd Channel & manually twist the head of the servo untill it is setup the way you want & find a way to lock on a horn & secure it to hold calibration.

The PCB on a servo will put out voltage inverse to the center of the head & the radio adjustments.

Last one I did was set off of the 2nd Channel & I had headlights forward & brake lights backwards.