Henry's (Toronto, Ottawa, ...) has it for $8.99 for 36 exp and $6.99 for 24 exp (ouch!).
Kerrisdale Cameras (Vancouver, Victoria) has 24 exp for $5.99.
The Camera Store (Calgary) has 36 exp roll for $8.18 (ouch again!).
Lozeau (Montreal) has 24 exp for $6.99 and 36 exp roll for $7.99.
Those are some of the main Canadian stores (Henry's and the Camera Store particularly). Don't know about stores in Quebec City or the Maritimes (except Atlantic Photo Supply, which didn't show 400tx). Other stores in Toronto are comparable and other stores in Edmonton are more expensive. It looks like Prairie folk are getting the best deal on Tri-X in Canada. I'm surprised, I always thought that Canadians elsewhere paid similarly to myself. I'd assume larger markets like Toronto, Montreal, and Vancouver would actually be a bit cheaper.
But I hardly shoot Tri-X anyways. I've long dedicated my B&W photography to Ilford. HP5 is the same price as Tri-X, anyways.