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If you're ok with Green Gas, buy an airsoft innovations propane adaptor and run it through that. Green gas is really propane and propane is CHEAP! The first link is an FAQ explaining how Green Gas is really propane, and the second link is to AI's own storefront for Propane Adapters. These things screw onto the top of Coleman Propane or similar style propane tanks. The only difference is it will smell as an stinky chemical is added to propane to alert people to leaks while green gas isn't. Another pro of using propane over green gas is that propane is stored in a safe manner. Green gas isn't. If you search around, there's pictures and stories of people leaving cans of green gas in their car during summer and the can blowing up inside the car. If you aren't from Canada, Airsoft Innovation Propane adapters are sold at most Airsoft retailers these days