h/t WRSA
Look, kids, while our love of unbridled caveat emptor capitalism is exceeded only by P.T. Barnum's (from whom the header quote sprung), anyone who buys "fuel thickener" for nearly $250/jug might as well take the family cow along too, to get some Magic Beans..
The traditional recipe for homemade napalm is 50/50 gasoline (any octane will do) and ordinary liquid dish washing soap. Palmolive retails for about $25/gallon, a savings of about $220 over the Magic Goo pictured above. You can substitute styrofoam for the soap in a pinch, but more stirring is required, it works better with diesel or fuel oil, and the quantity is arrived at by getting to the right consistency during the process. Every several gallons, dump in a jar of metallic (aluminum will do fine) ordinary craft glitter, which particles serve as condensation nucleii for the flammable glop. (If we have to explain condensation nucleii to you, you're already not tall enough to work at this lab bench station).
As the XL-18 flammenwerfer Throwflame sells (and don't get me wrong: mad props to them for making that beauty) boasts a capacity of 3.3 gallons, that's about $5 worth of regular unleaded, and about $35 worth of dish soap, and a few bucks for some glitter jars at the craft store. Which would only leave you with $200 still in your pocket by not buying the Magic Glop, above. But you do you.
We understand Throwflame's desire to part you from 245 bucks, but if they do so successfully, your 80 IQ is its own reward. And you're probably not bright enough to be playing with flammenwerfers in the first place. (Well, once maybe. But probably not twice.)
Suture self.