I am wondering if seedling heat mats would work? I googled how hot they get and apparently they get to the same heat as therapeutic heat mats for humans? And they are waterproof to boot? They have to be because they are meant for seedlings so they would be exposed to dirt and water. I am in Australia hence the 240v. And there isn’t an auto shut off that you have to circumnavigate.
https://www.kogan.com/au/buy/gobran...cone-heating-pads-black-au-plug-240v-7527976/
https://www.kogan.com/au/buy/gobran...cone-heating-pads-black-au-plug-240v-7527976/