if you build a heat stick you'll have what you need and it will be portable from vessel to vessel. it's just a heater element and some pipe that you can dunk in a vessel for electric heating.
(or search here for builds).
if you install the element into the side of the pot you'll need a weldless kit from someplace like bargainfittings.com. this has also been done a lot but requires drilling holes, finding appropriate fittings to make things water tight, covering the electrical connectors, etc.
either way, step 1 is to find out how much electrical service you have at your disposal (15 vs 20 amps @ 120v) and make sure there is a GFCI in the circuit for safety (and that it's properly installed).