How can I get a small, easy piece of electronics custom made?

I am a music teacher and I want to get a tuner that only shows the note that is being played. There are lot of tuners out there but I have been looking for a year and can't find what I am looking for.

All I want is something that will attach to an instrument that displays the note being played, and in the key F. It's for beginners so I don't want anything else on the display or at least to have the note name larger than anything else.

I know I can sell a boatload of these. Every middle school in the US would buy them. I have tried contacting companies that make them but they are all in China and have no interest in doing any kind of custom work.

How can I go about getting this made?

I'd go talk to a guy at Radio Shack. They might have something on the shelf that can be altered to do this.