If you want to ensure that your patent will not be leaked, you can only divide your product into several parts and give them to different manufacturers for production, and then merge them together. In fact, patents are not so mysterious now. Yunnan Baiyao, for example, is a state secret formula at home, and it is still the same abroad. That's the reason.
If you want to choose a manufacturer, you can sign a contract similar to a confidentiality agreement, so that you can have a bottom in your heart. If there is any infringement, you can bring a lawsuit to the intellectual property court.
I wonder if I can help you. Ask me if you have any questions!