So I have a 30qt Sterilite Rubbermaid (I swear I thought it was sterilite, exact same design...) container that I can use as a gas chamber (original lid is intact, I have a hole in side for water bottle already, was using it for rat transportation), and was trying to find the most cost-effective method of making a gas chamber.

As a note, please do NOT ask if I am near a [insert store here]. The answer is no. Unless you actually live near Houston/Smithers British Columbia, it is extremely doubtful you know of a store that is near me, so any suggestions of the sort aren't actually helpful.

Anyways, to the actual question, would using something like this produce enough co2 to actually euthanize a bin full of rats?
It uses bottles of baking soda+citric acid (or similar) to produce CO2.

The closest business that refills CO2 that I have found is a 3 hour drive away, although I am (and will be) looking for somewhere in Smithers (which is still a 45 minute highway drive away), but if this works it would be more convenient for me. My other problem is trying to find a regulator for actual CO2 canisters that isn't overly expensive in canada (amazon.ca prices are a bit ridiculous, and the ebay link in another thread I saw doesn't appear to ship to canada).