Like vargy said, get one from working parents. Go watch the parents hunt, see if they do what you expect the parents to do. Find a hunter, not a breeder. Whether or not they have dogs for sale or breed, they will be able to point you in the right direction.
What do you plan on hunting? A good JRT is hard to find in most areas, but they are out there. There are a ton of them for sale, but from backyard peddlers that could care less about hunting them, and more about the cute little things. A good JRT will hunt barns and piles, holes, etc. Where are you located? I will see what I can do to line you up with a hunter with real working JRTs.
Nate