Cat with urinary tract issues litter problem

Hey all, I have a cat who’s been on the Purina Pro Plan UR Urinary St/Ox dry food for a a couple years now. He used to have issues with crystals in his pee, but the food has helped him out a ton (expensive but I recommend it if you have this issue) The problem is his pee seems to never clump properly in the litter box, it always breaks apart when scooped and I have to completely empty out the litter box almost every day. Has anyone had a similar issue and does anyone have a better litter suggestion? I have tried the Breeze pellet litter boxes, but I think the hard pellets are something he doesn’t like as he started peeing on my clothes. I’ve heard that horse pellets work well, any advice?