Well there are several ways to accomplish co2, yeast has co2 produced(sugar/ but it is not controlled therefore would go 24/7 not really a problem but a waste. Brewing beer, also does it and you can readily get supplies and enjoy a cold one!! There are a couple of "buckets" which also do the same thing. I would first look at getting a tank/regulator and a timer, they are to be had on Ebay for reasonable prices. BTW a used co2 tank works as well as a new one but for less $$. I bought one (20#er) and its been 6 years!! You need to re-test them every five years though.
To make homemade; get a 1 gallon container with a lid, use 5 cups sugar add yeast according to directions on package, put a few small holes in the lid. After a couple days shake the crap out of it and co2 will release into your environ. This will last a week or so.