Brake light switch...

Does anyone have a clue how the little sliding part of the brake switch mounts to the brake pump (Front brake MC)?

The bike is a Suzuki GSX400 but the switch is the same on all Suzukis from the 80´s.

I´m not sure what´s wrong with it but the slidig part fell out when I unbolted the 2screws holding the switch to the brake pump and I can´t put it back together as it is, it simply wont slide when I apply the brake