I buy mine at canadian tire, they have huge one. Try the garden center of a hardware store. My garden store also has some but they only have 1 big bag in the back store and it's more expensive. Did you ask if they can order bigger one? Usualy they don't keep those cause nobody need so much!
www.Hiss n' Herps.ca
0.1 White-lipped python, 1.1 Dumeril boa, 2.2 color phase Amazone tree boa, 1.1 Borneo short-tailed python, 0.1 Red blood python, 1.0 Ambon mollucan Scrub python, 2.3.1 BCC, 1.0 Irian jaya carpet python, 0.0.1 Mangrove monitor and 1.1 Bearded dragons