Well....
A reasonable purchase would be a thermostat, 2 hides, an Acu-Rite thermometer/hygrometer, some foil and duct tape to cover the screen mesh lid, a small water bowl, and maybe some sphagnum moss.

-Reptile Basics (http://www.reptilebasics.com/Thermostats-p-1-c-250.html) has a good selection of thermostats.
-Lowe's carries the Acu-Rite digital thermometer/hygrometer (it is not reptile specific).
-Hides can be made from lots of things (planter bottoms, bowls turned over with a door cut and melted in, etc.)

If the room the snake is in is chilly, you might want to put some cork board or insulation around the sides and back of the tank to help hold in the heat. At any rate, you'll want to darken the sides and back of the tank with paper so that the ball python feels more secure.

This is a great info sheet for glass tanks: http://www.ball-pythons.net/forums/s...ad.php?t=56846

Good luck at the vet