Sunrise, Yallo and Lebara are all from Sunrise (at least using the same network).
But: Between the Sunrise, Yallo or Lebara, calls are not cheap anymore.
Only on the same network (Sunrise to Sunrise, Yallo to Yallo etc.), the calls are still cheap.
Options: Aldi, Co OP, Migros etc sell cards.
Behind the airport, there is a Media Markt.
I am sure, you will find sunrise at least there.
CO OP often also has sunrise brances.
www.sunrise.ch will be your friend.