You can use NIX or RID cream rinse to make a weak permethrin solution by mixing the 2 oz (59 ml) bottle very well with one gallon of warm water. Put the solution into a clean spray bottle and use it the same way you would use PAM - spray the enclosure, dampen (don't soak) the paper towels, and spray the hides. Do NOT spray the water bowl or the snake, you can give your critter neuro damage from permethrin poisoning. Once everything is dry you can put the snake and water bowl back into the enclosure. Keep some treated and dried paper towel on hand as well so when your snake makes a mess you can change the paper towels quickly.
PAM is 0.5% permethrin. The NIX/RID solution is much weaker, but since it comes out of a spray bottle rather than an aerosol can and you use more of it, there's also enough permethrin on the surfaces to kill of the mites.
I don't use the oil treatments as they can cause scale damage. A mere drop of dish soap to break the surface tension so the mites will drown in a water bath is enough.
In the future any new snakes should go into a pre-treated enclosure when they come home; during the quarantine period you should assume they have mites until proven otherwise. In fact, the first thing I do after unboxing is wipe them down carefully with a paper towel that I've sprayed with Reptile Relief/Reptile Spray. My vet suggested spraying the paper towel and wiping the snake with it, as opposed to spraying the snake directly, as most snakes hate to be sprayed and you end up with more product on the floor of the tub, the carpet, in the air, etc. than you do hitting the snake. Plus, you can treat the areas under the chin and on top of the head while avoiding the snake's eyes and heat pits.