I am a native Chinese, a professional translator, and also a sourcing agent,
fluent in both Chinese and English language
currently living in Nanchang City, capital of Jiangxi Province, China,
You are right, it is better to do business with the manufacturers directly than with the trading companies.
I can do a research on the major Chinese e-commerce websites, where most of the big BOPP film manufacturers sell their products, and then give you a report specifying their FOB prices and contact information.