To find china spectacles manufacturers in America, the best way is to find them online through some ways. And usually, Alibaba is a good site to go for looking china spectacles manufacturers. Just search keywords like China eyeglasses, China sunglasses or China eyewear, there will list you some China manufacturers specialty in spectacles. Hope this help.
It is not that hard to find China spectacles manufacturers. First, you google it, and you will see a large number of eyewear manufacturers in china such as https://www.aliexpress.com. These chinese eyewear are at wholesale price. It is well known many things made in china are quite cheap and in good quality. If you don't find a good producer in aliexpress, you can find many others Chinese B2B, B2C websites that sell eyewear.