A friend of mine had an electric element welded into a discarded propane cylinder. That generates a tonne of steam, and you can set the steambox on top of the tank. It makes for a somewhat precarious balance unless propped, but the steam source is centred for even coverage.
I started with a Coleman, but kept running out of fuel at the wrong times.
I switched to a "turkey boiler" burner, lots of heat, and a 20 lb LP tank runs forever. I actually use a modified 5 gal steel can and place it on the burner rack. The can has a hole with a 3" pipe in the top. the steam box is on legs and is just above the can on the burner, with just a short extension between the can and box.
I use the propane tank with a heater element. a 220v heater makes more steam than you can shake a rib at. A 110 V unit works too, but is slower to come to full heat. I've got a cobbled up T-fitting with a dishwasher hose running out the side arm to feed steam, allowing it to be recharged from the top of the T.
I have two wallpaper steamers with their attached hose system that I picked up (well one of them) at the Habitat Resale store for $10. The other my daughter gave me. These are self contained units.
I have a 30k BTU canning burner attached to a 20lb tank. I use a 5 gallon stainless steel beerkeg that I pressurize. Due to the elevation I am at, I have to run a pressurized system or I just don't get to steaming temps. I hit 205 pretty easily. Without pressure, I get about 175. It is far worse in Wyoming, with an elevation of 7500 feet.