Thank you, that's probably the simplest plastic recipe on Youtube.

How about potato starch? It's very hard to find corn starch in the country I live in but almost every supermarket here has some potato starch available for about $0.8 per 500 grams. And yes, it gives good results too. The same mixture you've shown but with potato starch results in rather sturdy (and clear, if everything is done perfectly) plastic. Considering plexiglas is expensive now, case-modders can cook it themselves. :D