How do I find a company to produce a small plastic educational item?
To test this, you could create a prototype or a small production run and then hit the educational expo and/or trade show circuit to demonstrate or show your item. Only then can you gauge if there truly is any interest or a market for your product.
If there is, you can work getting the legal aspects of your invention squared away, and you can also work on cutting your production costs by looking at global options (China, India, Indonesia) for long-term manufacturing.
All the best.