You could just buy a heater, cut the cord end off and send it through the wall. But the male cord replacement part at home depot or lowes. It has a little screw you remove to open it, clamp your wires down to the right sites and then screw it shut. Plug it in and your done
The item I'm describing is one of these http://www.amazon.com/Heavy-Duty-3-Wire-Replacement-Male-Electrical/dp/B003URJVPU