I know Saskatoon very well - used to live there for many years. Have you tried the Bulk Cheese Warehouse on Broadway? Not sure whether they would have it but it may be possible. Heck - any excuse to go to the BCW is a good one! I agree with Bob - you will likely find it in one of the grocery stores.
I am not sure about "ToonTown" as I am in Edmonton but I acquired the bottle I have ...Borges brand from Spain... from the vinegar section of one of the major supermarket chains, i.e. Sobey's, Safeway or Save On Food so I suspect the same likely holds true for Saskatoon.
Tarragon vinegar is not too "exotic" so I hope a local outlet stocks it.