Hey you can get duster gas from staples business depot. I got some today and tryed it in my Berreta and I found that it sucks propane is the way to go. Also you can get the multi adapter butane cans at Home Hardware for filling your mages with Duster gas like shown on this website.
I know some people where asking where to get the adapters. Also using one of the adapters that come with the butane you can refill the butane cans with propain. But you need to make an adapter that will fit on the end of a propain torch. I will post detailed pics later this week when i fined out an easy way to make the adapter. you can also get rilly small butane cans with the same adapter that is used on the green gas cans at Canadian tire and they can be refilled with propane for use in the field. And there easy to carry around in your webbing.