Kingston is a small city and doesn't have any international flight except a few to the States.
Event in Ottawa or Montreal, people have to fly to China via Toronto or Vancouvor.
I usually buy tickets from TianBao (http://www.tianbaotravel.com/chs/) or China Travel Agency (416-979-8993). You can buy it from Toronto without any problem or trouble. They can issue you electronic ticket by email or fax.