You will find souvenirs all over Beijing! But there are some places where souvenier shopping is even more concentrated.
Wangfujing Street and Nanluoguxiang there are stores selling crafts like Chinese knots, chopsticks, jade jewelery, novelty T-shirts and more.
If your keen to do some bargaining head to places like the Silk market/hongqiao Market as well. You should aim to get 50% off the asking price.