Looks like the Guild online shop sells replacement tuner sets for both the GAD Series and The Westerly Series guitars. So all you need to do is figure out which one you have and order the proper replacement set. You might be able to call Guild and talk directly to someone about purchasing one tuner only but I am not sure if they do that. Also if you bought it new and can prove that you are the original owner it may be under warranty and they may just send you a replacement tuner for free. Here is the link to the Guild Online shop Westerly series and GAD series tuner page.