small heated enclosure

Hello,
I'd like to build an insulated box for fermenting kombucha and it needs to be maintained between 75 and 85 degrees Fahrenheit. It would be passively ventilated. I've found various heating elements that look like they'll do the job, plus many thermostats, but most of them are line voltage types and I need something I can plug the element into and that will also be positioned on the outside of the box. Ideally, it would be digital but that might not be necessary.

Would anyone have some ideas about what I can use and how to do this? I'm unaware of whether a line voltage thermostat can be wired up with a plug.

Thanks,
Rob