Co2 Supplement for grow tent

Hello i current have the exhale co2 bag in my 4x4 flower grow tent and i am expanding and getting a 4x8 tent aswell. I was wondering if anyone has any advice on a good co2 supplement that will be good for this space... I know there are many options bags canisters etc just not sure what is best.

I suggest 20lb cylinder with solenoid valve. CO2 controller. Done.