I do use a tube heater and it does a good job but it's a big one in a big insulated box.
For one tort you can do the same thing on a smaller scale and you could use either a small tube heater or a ceramic heat emitting bulb .
There is another heat bulb/emitter that I think Jonathan has purchased but not said if it's any good yet but that's probably due to not needing to use it yet.
https://www.arcadiareptile.com/envir...eat-projector/