Wiring for steam generator control

Hi,
I am building a sauna steam shower. I have not decided on a particular steam generator yet. However, I would like to proceed with the bathroom and finish it.

I would like to wire a wire of some sort for the control unit (temp controller to the steam generator). Is there a recommendation of type of wire I should use?

I already have a copper pipe roughed-in from the intended location of the steam generator to the shower.

Thanks,
Van