EINs issued to public companies are publicly available and can be obtained from SEC filings.
See https://www.sec.gov/edgar/searchedgar/legacy/companysearch.html
EINs issued to private companies are available through searches on some state authorities' web sites. For example, EINs for businesses registered with the State of Florida are available on the Florida Division of Corporations web site.
https://dos.myflorida.com/sunbiz/search/
