I ordered all 3 of my CTR's from the States and had zero problems. When I first got my AR15, I decided that I wanted options so I ordered a Tan CTR, a Black CTR, and a Foliage Green CTR, as well as matching MOE grips in each color all from the States.This was in November during the ITAR troubles and the US election firearm frenzy sales, and still my order was perfectly legal.
I wouldn't worry one bit about Canada availability, the only thing you need to know is whether it will be cheaper to order over the border or to order from Canadian retailers. More often than not it's cheaper to order from the States. Sorry local retailers. Example, Magpul MOE stock and buffer tube are $220 at Dlask, I built the same thing for a friend for $110, and that includes the shipping and the cross border taxes you pay at the door to the Canada Post dude. Thats a $120 difference.