This is only half of a suggestion: conditions indoors must be favorable to the spider mites, if they are thriving. If you can change some condition they need, they may go away on their own.
But I don't know what spider mites like or don't like!
If they need it to be dry, you could spray them 2-3 times a day, or build up humidity with a saucer-and-pebbles and.or tent of plastic film. And take them into the shower occasionally and spray hard on the leaves, especially while holding it upside-down (and clogging your drain with potting mix).
If they need it to be moist, oh well, don't spray them other than with soap-and-alcohol.
If a fan keeps them from settling and staying, run a fan.
But it isn't a whole idea until someone more knowledgeable tells us what spider mites like and hate.
Many decades ago, I reluctantly used malathione to reduce the number of spider mites. Now I wouldn't use an organophosphate to save a crop's life. If you put the chemical-structural formulae next to each other, of organophosphate insecticides and organophosphate nerve gases, the differences are so slight they are hard to see right away. A friend who did a paper on that had three categories: organophosphates designed to be war gasses, organophosphates used as insecticides, and organophosphates that were BOTH.
What an ironic instance of "swords beaten into plowshares"!
"I invented this really potent nerve gas, but it is so toxic they won't let me use it on enemies in wars!"
"Don't worry, sell it to Monsanto and they'll spray it on our food crops."
Bon appetit!
