I've seen the bags at Jumbo and Carrefour. Of course, you will never find more than 5 or 10 bags in a container, they sell them in little bags of 5 or 10. I've searched in vain for a box of 50 or 100.
The real Ziplock containers area little more hit and miss, but I found some at Jumbo once and bought a bunch of them.
When I make a trip back to the States, or a friend comes down, I always bring back or have carried a couple of 200 count boxes of various sizes...