Besides I'm not sure you could get the Napalm to mix with the gas in order for it to stick. Just gas alone will spray out and burn up in a huge fire ball but go nowhere. You need something heavier than gasoline to spray so it will go out. Also the ignition disks are expensive and you will need an air compressor as well to fill the air tank. Again expensive, dangerous, and no practicle use. Unless you need to get enemy troops out of pill boxes. Did I mention that the gas eats the gaskets and the hose and the things leak! If you want the same experiance go spend $22 bucks for a Zippo lighter and 5 for the fuel. Over fill the lighter. Go stand in the middle of the street with a friend holding a bucket of water. Open it and with the fuel on your hands srtike the wheel. See same effects for under $30 with no one else getting hurt.
Here is the Legal warning:
While the flame thrower may be legal with or with out a tax stamp, firing one may have you charged with arson by your local PD. Same goes for the tracer rounds, dragons breath, or the bird bombs. No if, ands, or butts! And if you think a handgun is expensive try renting a lawyer for a trial, even if you are innocent of breaking the letter of the law. Again go play with the ones on the Play station call of duty and do not worry about lawyers, doctors, skin graphs, Skin scrapings, if the food at the local jail is bad or really bad, or how your going to pay back the cost of what ever was accidentally burned when, not if, the wind shifts.