Just in case people actually think this is a good idea: do not. Plastic, uncontrolled spray, and blowback is just really shooting uncontrolled fire in all directions. It works in your cartoon world head, but I know someone who tried and suddenly the failure (like escaping fumes around the holder, gasoline versus rubber gaskets meant for water) make you go, "Oh. Right." Thankfully, they only got first degree burns on their face, head, hands, and arms, a weird balding patterns, and missing eyebrows. Thankfully, someone had an ABC fire extinguisher nearby. Yes, alcohol was involved.

The ones I have seen that work involve metal tubing and a secondary mixing of forced air along with a special fuel. https://www.recoilweb.com/flamethrowers-once-tools-of-war-now-toys-67763.html

Gas tends to dissolve/soften plastic.