Chinese Birth Certificate

I was born in China in 1958, and now a US citizen. As many Chinese Americans I have nearly reached retirement age, and for claiming retirement benefits in the US we need to show our original birth certificate. In 1958 I do not believe China ever issued birth certificates to Chinese citizens, and I am now an American citizen, where can we turn into for such service to obtain an official birth certificate and what is cost? Thanks, in advance, for your help.