Try this stuff - http://www.reptilebasics.com/mite-killers

My baby boa aquired mites at the expo where I got her. I talked to Rich at length about Reptile Spray. I was a die-hard PAM user too. Not any more! OMG, this stuff was amazing! And SO EASY to use. This stuff is so safe, you can actually soak your snake in it. The mites die immediately - this works on the exoskeleton of the insect and will kill mites and their eggs. I treated Pandora in our hotel room that night and did not bring home a single mite!! This works ON CONTACT and once she was wiped down with it, she was instantly mite-free.

You can put it directly on your snake, and wipe down their enclosure with it too. Spray it directly on the substrate and allow the whole thing to dry then put your snake in and you're done. I will use this from now on.