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Manchester is the best available, but there are cheaper options. Some people use two BBQ tanks, and have them connected by a Y fitting. That would be the cheapest way. Another option is to get a tank from a forklift, but be sure it's a vapor draw tank, and not liquid draw.
Most mfg's and dealers sell the complete systems with tanks. Sometimes you can even find one at a salvage yard out of a wrecked or abandoned motor home or travel trailer.