There are only a handful of places in Chinatown that serve peking duck, and it can be quite expensive. My friends and family used to go to Seven Wives before they closed down for business. You can get a duck bone soup, peking duck, duck meat with stir-fried vegetables, and a steamed whole fish for $19.99. That was a steal when you consider peking duck can cost $30 alone.
Luckily, there's still BBQ King House in the same plaza as Lao Sze Chuan. Unfortunately though, it'll cost you $30 for a similar package (used to be $19.99 also). You'll get a shrimp dish instead of the steamed fish.
You can also try House of Fortune.
BBQ King House
2148 S. Archer Avenue
Chicago, IL 60616
(312) 326-1219
House of Fortune
2407 S Wentworth Ave
Chicago, IL 60616
(312) 225-0880