L.N.
Our kids' room doesn't have heat duct run to it, and a space heater was out of the question. Being a contractor and electrician, my hubby found a wall mounted electric baseboard heater that he was able to run into our walls electric supply =no plugs. It has a temperature control, also. Some nights are still a little chilly so I have found that a humidifier helps ALOT. After all, that's what heat does is add humidity; air conditioning takes it out.
Good luck!
~L.