In Qinhuangdao, pearls of highly variable quality are used to make a variety of interesting products, including portieres, necklaces and bracelets. Do not expect everything to be genuine, bargain hard, and be suspicious if bargaining works too well!
In Shanhaiguan, you will also find pearl products, and various local handicrafts. The street market on South Street is worth checking out, as is the clothes market (Yifu shichang).
In Beidaihe, shell work and other handicrafts, although not of the highest quality, can be bought from markets on the beach front.