Sally Beauty carries the peroxide cream:
https://www.sallybeauty.ca/hair/hair.../SLNCAR63.html
For simmering, I've used a bucket heater. 1000w is good for a five gallon bucket. I had a 1500 watt one, but it actually boiled the water in the bucket. Then it died. I'm guessing the steam did the electronics in.
https://www.amazon.ca/Immersion-UL-L.../dp/B07S95WHXB