I would also recommend using Nichrome. I made them for my SCT and my SN-10, complete with a controller.
I would stay away from using resistors as heaters, they are designed to reduce the flow of electricity but stay within heat stress safety factors. They will not really achieve what you want without making them hotter than their design.
The below link shows you everything you need to know including a calculator.
https://www.blackwaterskies.co.uk/20...-heater-bands/
The link below shows you how to make a simple, safe and cheap controller
https://www.blackwaterskies.co.uk/20...er-controller/
Everything you need is available on ebay.
Hope this helps