I answered a similar question here. Bricks-and-mortar shops generally have very little selection and identical prices to what's online and they will order for you from a catalogue. If you want to know what's available, check out the Badminton Market and Badminton Mart websites. If it's not there, it probably isn't sold in Korea. You could also check the Korean websites for Victor and Yonex. That might also show you what a shop's catalogue will have in it.