If he is suddenly footy on stones and wasn't before, might be worth having a look at his feet seeing if he has any thrush developing in his frog, or if anything has changed in his diet or grazing, even wormer can make a difference to their feet.
Boots wise I have tried a couple of makes with my horses, got some easyboot gloves at the moment, I always find the saddlery shop has a good range, a lot of people like renegades as well.