I was looking for exactly the same thing, you know for trail riding and stuff. Check out the Sports Medicine Boots that Pro Choice has. Their really great.
To get you're horse used to them, well he may not need to get used to them, my horse did just fine. But, if you need to put them on and turn him out with them on for a little while. keep an eye on him though. Lounging works as well. Its great to have boots on the trail, and these can even be used for trailering!!
Live To Ride!!
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Heaven Help Us by My Chemical Romance