Hey Sam, thanks for reaching out! We don't currently have filters to identify companies by series stage yet. Maybe sites like Ycombinator or similar sources could help create those list of companies that you can scrape with our Clay Extension (or similar tool)
You can then import to further enrich and find decision-makers with those parameters. Our getting started video shows how to find people a couple of minutes in, in case it helps -https://www.clay.com/learn/getting-started-with-clay