There's a product called Provent-a-mite which does the job extremely well. I had a recurring mite problem and tried various things, and PAM worked in one does. Plus, it's pretty safe when used exactly as directed:
Take out the snake and water bowl. (I put the water bowl in the dishwasher.)
Spray the cage surfaces and substrate until slightly damp, and let the cage air out until everything is dry. (I would completely remove particulate substrate and use newspaper.)
Put your snake back in the cage when it's dried out, and replace the water bowl.
Don't spray the snake, and don't spray the cage when the snake is in there. And it's probably a good idea to leave the snake's food items on a paper towel, lest they come into contact with the pesticide.
If you don't want to drop $25 on a can of Provent-a-mite, Wal-mart sells the exact same product in the exact same concentration (.50% permethrin), labeled as Equate brand bedding spray, for about $4.