Just a point of clarity. Improving on an invention is patentable, but that does not mean that you lose your temporary monopoly. They cannot infringe your patent with the improvement and then go to market. Of course you do have defend your patent if you find someone infringing, and this can lead to court cases. If you do not have familiarity with patent law and how to write patent claims, you will likely need to have someone help you. One possibility is to partner with a company that makes similar items and get a secrecy agreement in place to see if they might be willing to share costs (and of course profits).