If you're looking for something a little more "conventional" for housing your python, you might check some of the chain pet stores.
I picked up a new 20 G long terrarium with the "built in" locking lid at Petco this past weekend for $60. At the advice of a friend of mine who has raised snakes, I'm going to visit the hardware store this weekend and pick up a piece of thin plexiglass to cover most of the underside of the screen top (half the top is screen, the other half is hinged glass) to prevent any nose abrasions should the snake decide to rub against it trying to explore a way out.
Myself, I like the terrarium over the Rubbermaid box idea just because I'm still novice enough that I simply enjoy being able to watch my python as he crawls around the tank.
My friend used to buy the basic aquariums for housing his snakes. As he explained it to me, what he would do is remove the plastic top rim of the tank, then attach new glass sections to the exposed edges using Silicone caulking. As he described it, he would use 3 pieces. This would end up being the front of the terrarium, with the long sides of the aquarium now being the top and bottom. Along the bottom edge of the front he would attach a strip of glass that came up maybe 1/4 of the way from top to bottom. A similar strip would be attached at the top of the front, extending down maybe a few inches. Between these would be the "door" of the terrarium, attached with metal hinges glued to the bottom strip, and secured by a hasp glued to the top. He left just enough gap between the "door" and the fixed portions of the front to allow airflow into the terrarium. As he explained it, these were relatively inexpensive to make, secure, and convenient to access as he stored his terrariums on shelves, therefore front access was easier than top access.
Just some options to consider...