i know a bit about this subject. yes you can use beer keg tanks, they are identical. there are a couple of places that you can find tanks, welding supply houses (which is were i got mine) restaurant supply stores, some paintball proshops, and the internet, ebay is a good place. i actually found my tank on ebay and it just so happened that the place that was selling it was about 5 miles from my house, coincidence or what. there is really no point in buying a new tank because 9 times out of ten the place you get it filled will just exchange your tank, rather than make you wait and take their time to fill yours. i have had several different tanks. i dont know about other places but i got my tank for $60, it was used, but recently hydro tested. and as a matter of fact, i only saw the tank i bought for about 5 minutes, because when i told them i wanted it filled they just exchanged it. as far as fill price goes, its usually about $1 a pound. the gas is cheaper but they charge you a gas tax and some other stuff, so it works out to about $1 pound. MTA was right, with a 20 pound tank you will get roughly 660 liters of 100 psi, so cut that in half for a 10 pound tank. this post along with my how-to should give you most of the information you need. if you have any other questions though, dont hesitate to ask. this is something we havent really dealt with on the new forum, but once we do, we shouldnt have to deal with it again
TimB