I would suggest building a proto type and getting it working properly. Then find out what type of stores would be able to sell it. From there go to the local (mom and pop) type stores to see if they would have any interest. Don't try to sell it to them then, just find out if they would be interested. It would be hard to sale a proto type anyway. All they'll want to know is how much it'll cost them and how much it can sell for.
If you have enough interest in it then vist everyone again and see if you can get a letter of commitment (or intent to buy) from them. You still haven't sold anything yet but it is something you can take to the bank, SBA or investors to get a loan.
Once that is done you'll have to find a company that has the resources to build it or a bunch of smaller companies.
Remember the light saber when the movie Star Wars first came out. That guy's proto type of the light saber was a flashlight with a plastic golf club sleeve tape on.
Good Luck