You seem to be missing an important step, before you find a manufacturer you probably want to create a prototype. While the idea might be great in your head, you won't know if it's any good until you've built a few prototypes and tested them on your target audience.
There's a TV series in the UK called Dragon's Den where inventors pitch their ideas to angels to get funding. You can actually learn a lot from watching it (in terms of understanding if your product will actually suceed or not and various problems you might encounter). It might be worth your time watch a couple of seasons of it.
I am planning on prototyping first even though that may not have been clear.
There is a show in the US called American inventor which sounds similar to Dragon's Den (it probably is the same thing adapted for the US, like American Idol).
I have seen American inventor and you do learn a lot. The biggest lesson is not to spend too much on something which may not sell. I have seen people go on there and state that they have put their life savings or $50,000 to $100,000 on ideas which were not so great.
I have no illusions and tend to be pretty realistic. I think there is potential for my idea, but I would first prototype it and see if there is a market before building 10k units.
I've seen American inventor before, it's not quite like DD. DD is pretty much like a real VC pitch type of scenario, where you have startups that have got off the ground and are looking for funding to expand. So you get a lot more variety of companies and a lot more concentration on business planning. AI seems to be a lot more focus on "best invention" and is a lot more "reality showish" then DD.
There's a TV series in the UK called Dragon's Den where inventors pitch their ideas to angels to get funding. You can actually learn a lot from watching it (in terms of understanding if your product will actually suceed or not and various problems you might encounter). It might be worth your time watch a couple of seasons of it.