This helps you find the people you follow on Twitter on Mastodon. It assumes the Twitter profile publishes the Mastodon handle in their bio, user name, location field, URL field or in their pinned tweet. I added mine to my bio.
The tool found corresponding Mastodon accounts for about 10% of the people I follow. Most of them are colleagues in high-tech or people related to high-tech. I hope this improves.