Tips on Finding A Manufacturer Locally or Overseas to Manufacture Your Product 
Not all products need tooling. Maybe your product needs a seamstress, a machine shop, die-cutting, or steel welding. So, where do you find the companies to do this? I look for local contract manufacturers on Thomasnet.com and I also look for overseas manufacturers on a site like Alibaba.com. I ask other people that I network with who they use, like those at your local inventor’s club. Over the years, I’ve built relationships with different types of manufacturing in upstate New York, Colorado, China, Taiwan, and Vietnam and I feel like I can produce almost anything now!

When you’re searching for a factory, notice that there are trading companies, suppliers, and manufacturers that you’ll see listed. I like to work with the factories directly to get their pricing and not have to deal with brokers that markup the cost from the factory. A tip I’ve been doing for years: ask the factory if they can take you on a tour of their factory on a video call. I’ve even watched my products on video being produced overseas. I check to see if the person I’m speaking to is actually working in a factory or if they’re just a broker. I test them. I see if they’re a busy factory and, what types of people they have working there. I look at the cleanliness of the shop and if we can communicate well and they can understand me.

I also ask them to send me a sample of something they produced and experience a transaction, like how am I going to pay them, if they ship on time, and if they do what they say they are going to do. When the package arrives, I check how they packaged the item and I look at the quality. I also like to ask for references from other customers they’ve worked with. Sometimes they offer them to me and sometimes they don’t because of customer confidentiality. You can also find a local factory to manufacture with and you can physically do all of the above in person in the US. You have to find a balance between the costs of manufacturing locally vs. overseas, and the processes and comfort level are most important. You just want to make sure that you’ll have a good potential manufacturing partner for you and your product. 

Source: How To Make Money with Your Invention Idea book by Brian Fried