Very late as I just saw your post. I came across a website that sells plastic full size horse hooves that look very real. I can't remember if they sell other types or not. If you'd like the like link I'll see if I can find it. I have it filled away somewhere on a flash drive.
A pet food store or a Vets might have a selection of Hooves that get chewed by dogs. that is where I got hooves for my "Alien that Just Ate A Cow" costume.
The tricky part of using the hooves was my dog who kept wanting to chew them as I was sewing them on the costume!
I wore this costume to the second Haunted Attraction Ball that year.
The inside of the "Cow Head" I wore was a large empty plastic bottle that Wisk came in, the detergent. I covered it with fabric, nobody could tell it was a free, light-weight recycled item. priced Right TOO!