Most countries maintain offices of international trade. My guess is that there is a World Trade Center or equivalent organization in Seoul. Also, the Motorcycle Industry Council in the should maintain statistics for the U.S. You will most-likely need to join that group to gain access to their data. Also, the Radio Advertising Bureau should have some useful stats for you, but again, you will have to join. Go to the main campus of the largest university in Seoul and talk to a librarian. You will get more information than you can use.