Your best bet would be to start with realty agencies that specialize in Equestrian Real Estate. While within my searches I found real estate for sale, I did not see properties outright for lease (though my search was just a quick scan). A local Realtor specializing is horse properties, will have more complete local data and may know what local sellers are flexible & willing look into a lease option in the meantime.
Also I would suggest you inquire within you Equestrian Community, with other owners, shop owners etc, as they may also have some leads for you on possible availability.
Best to you in your endeavors,
Coach Realtors Assoc. Inc.