Polo Direct have a database for polo grooms and staff all over the world. In your request make it clear exactly what type of person you are looking to employ. Maybe you are only looking for someone that can drive an HGV or is good at riding young ponies. Alternatively you could be looking for team management or to run a yard.
Detail the employees responsibilities and location including the accommodation situation so we can get the best idea of what you are looking for and put you in touch with the most qualified people for your job.