For really advanced thrush, my vet and farrier recommend using a product called Clean Trax which you dilute with water and soak the foot in it for 45 min (we use old IV bags with one end cut off and duct taped onto the foot so you don't have to sit and try to keep the horse's foot/feet in a bucket the whole time) then take it off and dump the water out and tape the bag back on for another 45 min to let the fumes permeate the foot throughly. It's kills EVERY trace of thrush in every crevice of the foot. And an insider tip: our farrier recommends doing it with the horse's shoes pulled off because the Clean Trax solution will causes the shoeing nails to erode and may result in a loose shoe shortly after treating the foot. To prevent the thrush from coming back, make sure you're picking the horses feet throughly every day/multiple times a day if possible and try to avoid the horse standing in wet conditions if possible. You can also apply iodine to the hoof sole (avoid the frog or you can cause other issues!) daily then back it down to 3-4 times a week or as needed to help harden to hoof sole and ideally be able to prevent the thrush from coming back (:
It also depends on how advanced the thrush is - if you're just beginning to notice the symptoms then picking out the feet twice daily and spraying on apple cider vinegar each time can clear it up. If it's advanced (ie causing lameness), I would suggest getting your vet out as thrush can affect foot structure which is not something you want to mess with ☺️
one of my horses had terrible thrush, and what ended up clearing it out was washing the affected feet out with water everyday, as the bacteria don't like this, and then putting some hydrogen peroxide on the affected areas with a syringe. This really kills the bacteria. But to start thrush buster is also an amazing solution :)
Iodine in the hooves messes with oh in the hoof making it unliveable for the bacteria and fungi.
So you can probably get thrush in a chemist or pharmacy but to help cure the conditions try keep you horse on dry ground