An RHP should work fine. It must be regulated with a thermostat which will also help solve your problem.
Check with Bob at Pro Products and he will custom make the correct wattage for you. His panel is also the only UL listed one the market. His pricing is very competitive as well.
Don't forget to use two hides, one cool side and one hot side.
Also, you can add belly heat very cheaply for even more options and it will not effect the temp of of the cage except at the surface of the floor.
Lizzy, enjoying some warmth.
Herpstat thermostat considered one of the best.