United, Delta and Westjet Airlines have round trip airfares travelling from Boston (BOS) to Vancouver, Canada (YVR) for $321-$329, making 1 stop.
Departs BOS: Aug 28 thru Dec 7
Returns: wide and good availability, generally a 7-day stay works
Book on Expedia [expedia.com]
or Orbitz [orbitz.com]
. Be sure you note what class of service you will be on before purchasing. For instance, I checked a few and if it's Delta, it will be a basic economy fare.