Ok, I have read about the dry ice method, and the closest dry ice vendor I found is the same one that carries co2... Also 3 hours away. If you are saying baking soda/vinegar is done by some people, then that IS the answer to my question as citric acid caused the same kind of reaction, but is (at least in theory) cheaper than using vinegar.

Thank you for your response, I do appreciate getting an answer to my actual question.