The switches all come from the same "Peoples Headlight Switch Factory" in China. Buy one at any of the vendors. They do come apart and I have refurbished several by just cleaning the brass/copper contacts and wipers. Bending here and there or replacing a tiny compression spring to create more contact pressure. They are a simple slider switch with a rotary function for dome. If you don't want to tinker, buy a new one. I always take stuff apart that I'm going to throwing away just to see how it works and end up fixing it.
If it works by barely touching the knob it indicates to me as just dirty contacts. The sliding burnishes and builds a residue of black copper dust, oxidation and regular dust....... I.E. gum.


Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. - William Penn