Another option is to use a 0.5% concentration of permethrin. There is a version that is specifically marketed for reptiles, called
Provent-a-Mite. You simply remove the snake and the water bowl, spray the entire enclosure, let it air dry, then replace the snake and water bowl. There are a few select species of snakes that are hypersensitive to Provent-a-Mite, but boas are not one of them. I've used that product for many years, and it is very effective.
Alternatively, you can walk into your local Walmart or Walgreens and pick up a generic version (e.g., Rid). They are much cheaper, but they're also not specifically marketed for reptiles. I've used both, and never noticed a difference.