The receptionist here complained this week that she couldn't find Wunderbar chocolate bars anywhere. Sounds weird to me. I know that they're not the most commonly-found snacks around, but I haven't found anything to suggest that they're discontinued.
I did find places to get them, though. Go online!
Yup, there are web sites aplenty for people to buy Canadian candy. Hey, we have British import stores, Indian import stores, Chinese import stores and candy stores that specialize in American imports. Why not a shop for Canadians who miss Canadian food. (Even if the Canadian food in question is actually a Canadian version of a British thing, a la Cadbury products.)
To see one, check out Canadian Favorites, or their Canadian-spelled site, Canadian Favourites (which, oddly, seems to go right to an IP address).
And to our never-before-Canadian friends in America: you call them 'candy bars' -- we call them chocolate bars. And what we call 'pop', you call soda, or in some southern states, 'coke'.