[Alfonso]

In Spain for a shop like the one you describe you would say tienda de componentes electrónicos or tienda de electrónica but in this last case it can be understood as an electro-domestics shop as well.
For the electronic component I don't have a clue about the exact word, but I would try a descriptive phrase like interruptor térmico. Sure this will be understood by people involved in electronics.
But South America is far away from Spain... so who knows...
I'm sorry not to be able to give you a better information.