Leaking a cupful of radiator fluid daily still after replacing the radiator then later the water pump! What else could it be?
Are you sure it is the radiator? You don't tell us the car... But on mine, they are known to split the coolant reservoir and it only leaks when hot which means the hot fluid evaporates and leave very little residue. You need to check all the hoses, connections and the reservoir for any signs of leaks.