In the meantime, if you give your birds whole grain wheat, barley, or even wild bird seed if that's all you've got, together with some grit, then the action of grinding up the grain in the crop will grind up the coccidia there as well. You will still need something to destroy the coccidia in the gut but this will stop it getting worse.
If you have chicks and haven't any chick crumbs (containing coocidiostat) then again, feeding them whole grains from the start will prevent them getting cocccidiosis, as again the coccidia are ground up in the crop and never get any further to affect the gut.