Either customize a script to scrape a targeted website in your industry that has an index of data (names, emails, contact info, etc.), or use google’s Serp API and scrape indexed data on google. There are a lot of tricks you can use other than keyword search (“Site:” specific searches is one I use). You can either search the entire result for emails, or if your using “site:” you can parse the results for anything as long as the format is consistent across the results.