WR Display - website (Winnepeg and Calgary- new accessories only)
Vic Store Fixtures - website (Victoriaville and Mississauga- new manufacturer)
Store Fixtures by Westmount (website) (Edmonton, Alberta - new only)
Action Retail Outfitters (website) (Edmonton, Alberta - new only)
Westmount Store Fixtures (website) (Edmonton, Alberta - new only)
Mathews Display (website) (Victoria, British Columbia - new only)
The majority of Canadians aren't far from a fixture dealer or chance to buy from a closing store.
You can check craigslist (website) for store fixture liquidations or used retail shelving.
There's dealers across the country, peppered about. Across the border, Washington, Minnesota and Michigan have used shelving dealers. There's taxes with fancy names on the Canada Border Services Agency's (website) step-by-step importing guide. I don't think the fancy-named-taxes are deal-breakers...probably some paperwork, though.
While most Canadian retailers are in a reasonable spot to find a deal, you already know if this ISN'T you.
Broad, sparsely populated land expances are tough places to find a good deal on shelving. You can expect to pay for your high Canookery with expensive shipping costs.