Can you get shavings for his stall? That tends to keep their feet dry (in fact, it does such a good job that we have to watch our horses here for dry hooves . . . everybody here uses shavings because they are free from the lumber mills).
I use shavings when we bed the stalls, right now they are stripped to just the rubber mats because I’m actually encouraging them to get out of the barn and bed outside. They aren’t closed in at all.
I do bed it with shavings in winter when I want to give them a dry place to stand and lay down inside.