if they were in veg it would be easier to combat or close to harvest you could have let them finish but at this point everything you do will hurt the flowers and your options are very limited because everything you use will leave a residue.
my suggestion is get a vacuum cleaner fit the end of the hose with a screen to keep it from sucking the leaves in and vacuum the whole plant. under the leaves and around the buds. this will remove many of the spider mites. keep doing this everyday until you see significant decrease in spider mite population.
in combination with the vacuum cleaner i’d also drench the soil with neemazal solution. just once with a hefty dose. these action will probably not kill them completely but it’ll help control the population and give you a chance to ride it out.
after the grow is done you gotta clean everything and find the source of the problem.