You can purchase mobile CityPASS tickets for any destination from citypass.com.
In addition, you can purchase CityPASS cards onsite at attractions in Atlanta, Boston, Chicago, Dallas, Houston, New York, San Francisco, Seattle, Tampa Bay, and Toronto. (Please note that New York C3 tickets and San Francisco C3 tickets are available only as mobile tickets sold online.) You can also purchase CityPASS cards by calling CityPASS Customer Care.
You'll also find CityPASS tickets for sale on many partner websites.