Yes, green gas is just propane with silicon oil pre-added; you can do the exact same thing with a propane can from crappy tire -- and priming the adapter with a couple of drops o' silicon oil every two mags loaded...
(Although green gas makers add that lovely april fresh scent to the propane -- and propane suppliers add that not-so lovely sulfur/eggs smell as a safety measure. i.e. if you smell rotten eggs, your propane connection is leaky... But thats the only reason the smell is different).