Depending on where you live, you could find an electric element that fit your needs. To bend nicely a sheet of plastic without burning it, you need to apply a gentle heat on a concentrated area of the sheet until soften. Red hot element is not good.
The picture show a machine that I made for that purpose. I bought an industrial element of 330 watts, 220 volts but I run it at 120 volts. It gives a nice gentle heat without any control and it work well for different kinds of plastic.
Otherwise, again depending where you live, "spring" elements should be easy to find.
Alain