BlueSwordM compiled a really good resource for people trying to buy Li-ion cells around the world: Massive post on where to get lithium-ion batteries everywhere in the world! Look at Post 2-5 for info, And Canada Post 123
The USA has several well-trusted and fairly-priced options, so I think you’re in luck if you’re worried about counterfeit/mislabeled cells!
For example, Illumn sells button-top Samsung 30Q for $5.50 or Sanyo NCR18650GA for $5.99, which is the sort of cells you’d be looking for.