Thanks ShinyCard/Syncmaster! I'm by Midway. I didn't think about Brew and Grow.
I've been contacting local welding shops here and either they don't carry any small canisters or they asking over $100 for a filled 5 lbs tank.
I tried welding shops at first as well in Joliet, but their hours were M-F 8-5 and closed on the weekends, so they didn't work for me.
I believe Brew and Grow has 5lb filled for around $90, but the closest Brew and Grow to you would be either Bolingbrook or the one in the West Loop. Brew and Grow does exchanges of the CO2 tanks and when I exchange mine, I pay around $17 after tax for the 5lb tank. I'd also call ahead first because sometimes they might not have any in stock if they all got exchanged out. The one in Bolingbrook gets their shipments on Thursdays, if that helps out at all.
If you are looking for a small CO2 tank, you can get a paintball CO2 tank. Not sure what size tank you are going to be using it on, but if it's for a nano, the paintball tank would work. You'd have to buy a special adapter
to get a regulator on them, but I think it's worth it .