Another option is a radient heat pannel. They work great and don't dry out the cage as bad as a heat light does. I have one in my boa master. Their a little pricey but we'll worth it. Heats up the cage anddoesn't get hot enuff to burn your snake.
http://pro-products.com/pro-heat/
That's were I got mine. U give him your tank info and he will tell u the one u need and will walk u step by step when u get it. Tell u where to place it and everything