There will be a Baby Fair at CoEx Mall from August 21-24. The Hypnobirhing instructor mentioned that it was good and my new friend Sharon brought it up as well so I am going to check it out. Maternity clothes and all things baby, including cloth diapers will be represented. I think it will be a good sampling of what Korea has to offer.
The website is all in Korean, but I clicked around and found "foreign visitor" page where you could pre-register so that you can enter the exhibit without being charged. I'll let you know if it works!