Where can I buy surgical tubing for a water balloon shooter?

I don't think that I will need very much, but my friends and I are trying to make one and we apparently need some. I live near Flint, Mi and I was wondering where I could get some. I am cool with ordering it off the internet. I'm not sure if a hardware store would have it... Please help! My friends and I are going to make a SUPER BALLOON LAUNCHER OF DEATH! Lol