C.M.
Stacy,
You can buy tanks in many places for about $20.00. You'll have it on hand for many occasions that way. (Walmart, Target, Probably KMart)
You can also get balloons at places that have party supplies. I get most of mine filled at Krogers. Ask for "Super Flow" to be added to the balloon first. I had regular latex balloons last for days because of the Super Flow. Normally, they barley last the day.
I think it's much cheaper to buy the tank, personally, after doing both ways for years.
C.