I just received my tank/hose rig from Joe the other day and it's awesome I'm thinking along the same lines Dave regarding the travel tank. If I can save up the $ I may order one of Joes smaller "guppy" tanks for hunting use. Hmmm, maybe for my birthday Jeff
went to the local fire station where all the substations filled their tanks- no go because of liability issues. that's why i bought a shoebox. hose/adapters cost $110-135 plus the tank cost.
Try paintball forums of sites. They are your most likely place to get one. Amazon also has them. I think scuba shops will also fill them for you. Or if you are friends with a firefighter, he might. They use high pressure air tanks(HPA tanks) for breathing,