Shopping for baseball caps
 

Does anyone know a good place to buy Japanese baseball caps in Tokyo? I heard that Yasukuni street may have some sports stores, but I'm not sure if they mean sporting goods (fishing, hiking, golf, etc.) or if all sports are included (as Sportmart or Sports Authority in the Unites States) Apart from Tokyo Dome for Giants merchandise, where else would someone go buy these items? Thank you in advance of your answers.