I'm looking for a CO2 cylinder in the 10 pound size (I already have a 20 and a 5 but they are serving other duties). My local gas shop sells 10 pounders for 170 and I see new ones online for around 115 to 130 but I hate buying those because my local gas shop doesn't fill bottles, they only exchange for used cylinders. Therefore it's in my best interest to buy the cheapest used 10 pounder possible. I tried Craigslist but found none locally. Anyone have suggestions?