Hi Router,
Welcome to the forum. A wide range of people from many different backgrounds 'lurk' on here so I'm sure you'll get a few ideas.
You say you have a 'working prototype' - Have you really put it through it's paces, abused it, overloaded it, dropped it, kicked it, and sat on it, and has it it performed to your satisfaction all the time.
I would endorse the 'keep away from the big boys' philiosophy, and regretably, in the world we live in, as much legal protection as possible for your idea is necessary.
And finally (To answer your specific question) why not try to find a small local engineering company who has the resources to make the bits, and start assembling a few yourself. Then get out to the local 'boot sale' and see if anyone buys them.
I can guarantee that when people see it, if there's a problem. they'll tell you about it. On the other hand, if it really is unique and does a better job than anything else you'll soon know about it too.
Good luck with your idea, it's long road you've embarked upon so don't get downhearted, just take your time and stick with it.