There's an interesting book called Poorly Made in China which goes quite in depth into some horror stories about products made in China and how hard it is to insure that they are of high quality. It is worth reading if you are planning to do a lot of trade with China. The author of that book, Paul Midler, had exactly the job you are speaking of, as a representative of foreign firms who needed someone in the country to inspect and review local factories to ensure the quality was high.
One way to find people who can do this is to contact your countries chamber of commerce, for example, if you are American, the American Chamber of Commerce in China, or your own countries consulate in the country. They may be able to introduce you to suitable business partners.