This fragility also contributes to their rarity, since so many did not survive. As both Thomas and Piers have said, good period maedate are like the proverbial hen's teeth. Since they rarely appear, there really is no dealer that would "specialize" in them. Kino is your best bet, but even then, you have to be there when one arrives because it's often immediately sold to one of their regular customers. On each trip to Japan, I scour the dealers (including Kino) and antique shops and manage to score the occasional piece. Good luck in your quest!