You could use a 100 watt ceramic heater as long as you put a cage around it so the snake can't burn itself. Other than that, you could use some simple party lights that you can get from Bunnings, they're about $1.64 each, 40 watt, I have 3 of them in my Olive's 4ft tank, and that keeps the temperature where its meant to be. That enclosure has 5 air vents, 2 at the back of the tank, and 3 at the front of the tank.