The only kits - at least the ones that are basically finished except for the staining of the wood/put part A into slot B - that I am still aware of, that can be sourced in Canada are produced by Traditions. They have a Kentucky style and one they call a Hawken which doesn't really resemble a Hawken but is a nice looking half-stocked rifle.
The cost of their kits at the wholesale level are barely 50 bucks less than their finished rifles so the few guys that have asked, when quoted a price (I sell a few side locks at work), changed their mind.
The only importer I am aware of that will even bring them in is REDL Sports (Vancouver area). So if you are really after one you can google them, give them a call and find out if they have a retailer local to you that would handle the sale. REDL doesn't sell to the public.
Lyman does still produce their Plains Rifle kits (based loosely on a Hawken Rifle) but they only drop ship and won't touch less than a case lot. So might be really tough to find one on this side of the border - as a retailer I am not interested in a case lot of kits when there is almost no demand for them.
The Lyman kits can be sourced from Track of the Wolf (in the US) but they list at $500 (USD), plus shipping, plus customs/taxes - so again, can buy a finished one for less.
Pedersoli also produces some kits but I have no experience at all with them - have never seen one, and have no idea of the cost range. Marstar, who used to be a sponsor (maybe still is) is a Pedersoli dealer and may be able to at least answer some questions about the kits.