Look at an Airsoft Innovations Green Gas kit. There's an adaptor that fits onto propane cans and there's oil in it as well.
1-3 drops of oil in the adapator now and then will keep you gun lubed. If it looks too lubed...use the oil less frequently. Too dry...use a bit more.
Buy the green Coleman camping propane bottles from Canadian Tire, home depot, Lowes, etc...
It's as easy as that.
BUy green gas in imported cans if you want...not worth the expense to most people.