If someone could point you in the right direction they would. Here's an idea, go down to the lake where you would be likly to fish. Hang out with the guys fishing powerlines and ask them if they could turn you on to a place to get one or better yet how to build one.
Was at the Ed Shirley store in country side on Lagrange rd and 55 th st yesterday and on his for sale board is a card for a complete powerline setup including the tank ect. If you want to go there and get the number or maybe call them and one of the salesmen might be nice and save you a trip and will get the number for you.
Thanks to all of you for your wise words. I have to admit, sometimes this forum makes me lazy. I went looking for someplace closer to home than henry's, and the first place I called in the yellow pages knew exactly what I was looking for. For all you northwest suburban anglers out there, Dependable Fire Equipment Inc. located in buffalo grove will deliver a 5# refurbished CO2 tank for $75. That's right delivered, to my work in my case. The lady on the phone was most pleasant and knew just what I was looking for. Thanks again for the replies.