Hi Andrew,
There is a Decathlon store between Tetra Rouge and the first chicane on Mulsanne straight. Drivers left. A complete camping department reasonable prices. there are some resturants close to the track if you do not want to cook and down town is well worth the bus ride. The ACO store in the infield also sells a small tent which I recall looked quite good but do not recall the price.
Which part of Canada? I am near Toronto.
Canada Phil