https://www.e-mobile.ch/de/oeffentliche-ladestation-finden/ has a map, and so does the app from bikester. The SchweizMobil app also has some charging stations, though they are hidden among other service facilities.
However, you usually don't need charging stations. Do a lunch break (or a coffee break, beer break, ice cream break, ...) at a restaurant, cafe, bar and ask nicely if you can charge your battery while you're there. I tried that dozens of times, with a 100% success rate.