Windscreen washer button

My old Fiat 850 originally had a "spare tire powered" windscreen washer, i.e., a water bottle pressurized by the air from the spare tire, and a simple button letting the water pass to the washers. After more than 40 years this system is no more, and instead there is a "conventional" water bag and an electrically driven pump.
The conversion wasn't too bad, but the button and the way it was being held in place were in need of some 3D magic.
So I designed a bracket to fit the electrical switch (