When I was competing, I would get all the miniature plants for my terrarium from the Violet Barn (violetbarn.com). They have a lot of customers (Canadian African violet societies) this side of the border so ordering from them is safe and easy.

Though I haven't been there in years, I know that I saw some miniature plants once at Pierrefonds Nursery at 2175 Cote Vertu and Pepiniere Jasmine, and I actually bought some from Cramer when they were on St. John's. I haven't been to their Les Cedres location in ages but you might want to check there too, depending on where you live in Montreal.

Don't know any Canadian online sellers.