I can document fipronil/Frontline causing both neurological problems and death in an animal, so it too can be problematic. That said, I agree that it is an order of magnitude safer than permethrin/PAM.
Another option is a very dilute ivermectin solution. I do not have the calculations in front of me so DO NOT take this as gospel but I believe it is something like 1:1000 dilution of a 10mg/mL stock. At this concentration it is not dangerous to snakes but it wipes out the mites (and most other insects… and snails… and isopods… and springtails… and worms)