After a call with local Rivian support, it turns out you can't buy a Rivian charger outside of initial contact anyway. Next stop: Costco.
Still, I can't believe there is no longer any online parts or accessory support in Canada. There is not even a website or catalogue to see what's available...
From Rivian Customer support chat:
“Sadly, Gear Shop is not available in Canada and you will not be able to purchase a wall charger via Gear Shop. The only alternative would be to purchase on site in one of our Hubs or Service Centers.”
There is a service centre 10 mins from me, but no phone...