I had mites once, and what i did was use betadine. Its this antibacterial solution, fairly expensive (but hopefully won't have to use it much).
Use the betadine by mixing several drops into a few cups of water.
Use cotton balls dipped in the solution on your snake.
Make sure to rub ALL of your snake. make sure to focus on the eyes, the heat pits, and the cloaca. Then let the snake soak in the betadine solution for a few minutes or 2 to kill any stragglers.
In the meantime, buy a new tub that can house the snake reasonably. Line it with paper towels. get a new water dish too.
Bleach everything your snake has been in. let it dry 24 hours before using again.
The trick to dealing with mites is to not panic, and to be thorough
All the best