I buy mine at Davidson Fire Extinguishers sales and service, 144 Percy St, Ottawa, ON K1R 6E3, (613) 235-1629 - Open week days 7:30AM–4:30PM, call for weekend hours.
I got my CO2 from Praxair.
I bought mine at Davidson Fire Extinguisher at 144 Percy St, Ottawa, ON K1R 6E3 between Gilmour and James Streets.