I've bought them at the Kitchen Store on the Danforth, they had a wide variety of sizes and shapes. I can't remember the name right now, but it is on the south side near Logan. I also an ad somewhere that showed them at the Superstore.
Coincidentally, I just saw these advertised in the Toronto Life Holiday Gift Guide (on-line, Toronto Life). They featured the President's Choice brand at "Loblaw Superstore at 825 Don Mills Road. The picture showed 5 loaf pans or 4 square pans @ $10 per pack.