I'm on Vancouver Island and tried to get Co-op oil for my last oil change but was unable to source anything bigger than a 1L bottle. I called them up to ask about getting 5L bottles and was told they aren't sold anywhere on the island.
I'd say Co-op is the best option, being 100% Canadian sourced, refined, and bottled...and probably available fairly readily in large parts of Western Canada....just not for me.
There are several smaller brands that are Canadian. I recently saw a non-detergent straight 30 bottle of "Wakefield Oil" at Lordco and looked them up. They don't seem to make much of anything for gas engines but do have a diesel line of lubricants.
https://www.wakefieldcanada.ca/u/1/products-wakefieldProducts-diesel
Wakefield Canada is the blender/bottler of Castrol in Canada. They also distribute Super Clean in Canada.