David,
You're confusing the Coleman Powermax canister with the short,squat "camping gas" canisters used worldwide for camp stoves, etc. The Coleman canister is shaped like a large Robart air tank and contains an internal clunk and feeder hose/tube. I believe the Coleman canister is only available in the USA, and very rarely as of late. A trigger valve assembly was devised for the Coleman Powermax canisters to facilitate filling the onboard tank in gas start turbines. Your post description works for the "camping gas" canisters.
Rgds,
Art ARRO