Flextile brand mortars are sold by Olympia Tile. I havent used their products in quite a few years, but they are a good product.
I don't know what Flextile sells, for going over Kerdi/Ditra. Most people used Kerabond from Mapie...because it works.

You can buy it at Rona. Here is a product link
http://www.northlandconstruction.com/product.php?pid=1021.For going over cement board, Flextile has a thin set called #52. If you really want to buy it, make sure you buy the WHITE thin set..especially if you plan on grouting with a light colour.