I’m from China , a mechnical engineer,some guys talk about the issue about china maybe is incorrect.
firstly if you can find an honestly vendor ,keep secret is not a big problem.Firstly you can demand a NDA from your supplier;secondly,you can contorl your CAD files format,for example ,you can give them a picture with demension,you can get a rough price，if you feel the price is ok，then make a next step;thirdly,if you want a accuracy price，you can give your vendor a shrink file（proe can do this.If you have any question, you can reach me,I will help you.