I have a telecaster and want to add a S-1 switch to it like the one the Telecaster Baja comes with. I've been searching the internet looking for a store that sells that switch but couldn't find any.
Do you know where I can buy one?

You can get a similar sound by wiring the tele for a four-way switch, so you've got the pickups in both series and parallel. I think the S-1 system is useless beyond that, if you want to sound more humbucker-y try rolling down the tone knob a little.