Where should I request for my birth certificate? Urgent!!!

Hello;

I know this question has been asked many times in many ways, my case may be different. I was born in Beijing and moved to Tianjin when I was 2 years old. Then I entered college in Hefei, Anhui provence. After graduation, I went to Canada and became Canadian citizen. A few years ago I moved to california and now applying green card (preparing I485 right now). But I don\'t have my birth certificate and I don\'t have my Hu-Kou either. Has anyone had similar experience before and how/where should I request for birth certificate? My understanding is without Hu-Kou the local police won\'t issue BC and consequently can\'t be notirized. If eventually I just can\'t reallocate my Hu-Kou, how do I get around BC? How effective is BC affidavit? (I drafted one for my parents to sign, but my laywer said it is the last resort...

Thanks in advance for any suggestions.

Jing