Sep 7, 2017 - 9:50 AM
Hi Blechlerm, and welcome to MySwissAlps!
If you want to buy it in person, be sure to ask for a Swiss Travel Pass. A Swiss Pass is something different for Swiss residents. You can buy a Swiss Travel Pass at any staffed train station, including the airport, but the ticket desk will be closed by the time you get there. It is much easier to print your pass at home and skip the ticket desk, with a possible queue, entirely.
You'll find all purchase options at www.myswissalps.com/sw isstravelpass/price. I'd recommend to go to www.swissrailways.com/ en, click to the Swiss Travel Pass, and fill out passenger details and the start date (September 22). After filling out your address, they will show the delivery options. Pick "Online Ticket" from the bottom of the list. They will e-mail the pass within 1-3 business days, but often within hours.
Note that a 3-day pass starting on September 22 does not include September 25. You need a 4-day pass for that.
Enjoy your trip!