I'm taking in a rescue ball python pretty soon. A friend of mine, who works a job cleaning out and restoring apartments, found a young ball python abandoned in a tank. She literally cannot find anywhere else to house him so she's giving him to me. I have a big 45L x 18W x 12H plastic cage. It is my ONLY available housing unit for the ball python and is actually the smallest unit I have (all of my snakes are larger adults.) And this is obviously waaaaaaaaaaaaaay to big for a little baby that will definitely feel insecure and not safe. I have to save a bit of money before I'm able to purchase a smaller cage or tank.

-Because of my mothers and my sisters insecurities over snakes, a tub unit is not doable. My family has a huge insecurity that the skinny baby ball python will escape and eat them all alive. So a caging unit is necessary.
-It will be a few months until I'm able to save the extra money for any "cage" type unit, because I'm currently paying a million and one different things off and only have enough money for an emergency vet trip if needed.

The way that this cage is manufactured, I can't install a divider without it being a huge hassle.

So basically, my question is this: Any suggestions for making the way-too-large environment more secure for the baby ball, without making the cage impossible to clean? I want to make the environment as stress free as possible for the baby.

Extra note:
The smallest UTH I have available is kind of large too. Ultratherm, 11" x 23".
I don't want to roast the kid if he doesn't feel secure enough to travel from the hot side to the cool side.