Patents won't save you. Trademarks can help you prevent imports like this, but nothing will ever stop your product from being sold in other places, especially mainland china.
No, my point is you need to find people who won't steal from you, not because you have patents, but because they're not scumbags. Going to Shenzhen, the odds are very much stacked against you with this.
Do small fly-by-night factories care about reputation? No, probably not. Does having your stuff produced elsewhere given this reality protect against its copying? No. Realistically, we just have to recognize that the exclusive right to produce something does not exist, except as vaguely enforced at retail through certain developed markets' monopoly-assisting enforcement arrangements... if you have enough dosh for lawyers to back it up. From a business standpoint, the cold hard truth is that producing anything physical is more about the object's distribution and marketing than the design and production, which can be monopolized only temporarily.