I am an employee of a privately held company. I have lost one of my stock certificates. How can I replace it ?

I know that for publicly traded companies, one can do a ';stop transfer'; against the missing securities which helps to prevent someone from transferring ownership from your name to another's name. But how do I replace the stock certificate of a privately held company ? At present the stocks are not traded even within the company. I just need to replace the certificate, in case the company goes public or gets bought over in which case I can cash out my stock.