Thermostat...
And don't use a fish tank!
That would solve all of your problems!
Animalplastics.com: t-8 or t-10 with a divider. Keep on one side until he/she has grown, or for a second snake.
Herpstats 2: controlling two different temperature admitting settings.
Radiant heat panel.
In the end you'll spend... About $500 on the set up. Extra items will drive the cost up. Bare bones would cost you... $300.
Crazy to spend that much? No, I have it to where the only maintenance I have to do, is clean, feed and water.