How to heat up a barrel drum?

I am experimentalist, and I am unsure on how to proceed about a question I have for an experiment. In the experiment, I would like to heat up a drum barrel like:

It is made of HDPE, and I would like to heat it up in a region between 80 °C to 100 °C.

I have seen options like this: https://www.vulcanic.com/wp-content/uploads/2017/03/drum-heaters.jpg

Do I have any other options?

I will be using this barrel to heat up a few grams of chemical pellets, so main objective is to make sure the vapor has a consistent temperature of the chemical of my choosing (e.g. iodine). Barrel will not be containing any liquid etc, just air.

I would like the air inside the barrel to maintain a consistent temperature.

• The challenge of heating it from the outside is the slow rate of heat transfer relative to the volume. If something is happening in the barrel that is generating or consuming heat, it will be hard to maintain uniform temp using just an external heater/cooler. – Andrew Jun 3 at 12:46

Assuming you want to generate vapors of iodine at ambient pressure, you need to surpass its boiling temperature. Wikipedia's box about iodine's physical properties state about $$\pu{184 °C}$$ for this phase transition ​(about $$\pu{364 °F}$$).
You intend to use a barrel made of high density polyethylene, HDPE. Wikipedia's entry for a typical specimen of HDPE mentions here a melting point of $$\pu{130.8 °C}$$. Because this temperature is about $$\pu{50 K}$$ lower than the boiling temperature of iodine, a barrel made of this material is not suitable for the intended experiment this way.