At one time, this operation was offerring horse rentals out of McCall, Idaho: www.montanahorses.com
He seemed like an honest guy when I talked to him, although we never ended up renting ponies from him.
God bless your search
There are people in Boise who will rent llamas. You can't ride them, but they are easier to get along with than a horse, easier to transport and you don't have to water them every day. They are WONDERFUL hunting animals.