It's best just to buy from them directly. Most used ones aren't going for much cheaper. They are a little pricey but you definitely get what you pay for. They are of extreme high quality. Obviously I love mine. They aren't for everyone or every horse, but it's definitely worth having one in your collection.
Cheapest place is right from supplier. They have a Facebook page. Mouthpiece, depends on your horse. I have 3 different mouthpieces for different horses, (chain mouth, 3 pc dogbone with roller, and 3 piece with port).Work super for me.