Ok, then you need to find out where you're losing that coolant, not buy a new radiator.

Drive in the garage, or if you dont have a garage then get a bunch of newspaper or cardboard and drive over it. Turn the car on, and let it get hot to the point that the gauge just starts rising over the middle. Quickly check for drips under the car. Turn the car off, check some more. Listen to all the different hoses for bubbling or hissing. Poke and wiggle the hoses to see if they are secure. Stick your head next to the passenger side of the engine, there are a bunch of heater hoses and the FIAV hose there(at least on a 4g63). Check the lower drivers side of the radiator, the stop-cock may be damaged or loose. Check the inside of the car under the dashboard for wetness (heater core).

look, listen, and smell lol and you will find it...