There are two shops I've dealt with in the Toronto area. The one I started with was AAA Surplus on 199 Baldwin St (Kensington Market). Just a warning to anyone heading down that way, the staff are not very knowledgeable at all. For example, I was asking for combat boots and was handed a pair of air force boots (safety type, not sure about the exact name) and ankle boots to try on. As well, after asking about OD107, specifically, and they suggested I get some crappy imitation MARPAT. Haven't been back since.
Not the easiest to get to, but definitely worth it is The Little Army Store. Staff are knowledgeable, helpful and they have a huge selection for such a small store.
The Little Army Store
20 Bermondsey Road
East York, ON M4B 1Z5
(416) 759-8038
Cheers