Use Discovery / Marketplace. Search by Instagram username directly or use the discovery filters (followers, engagement, keywords, bio, audience credibility, account type, contact details, location, interests, brands, last posted).

Discovery creators aren't on the platform yet, so they'll need to join before they can accept an invitation. Use the Must have an email filter if you want to be able to reach them automatically — without a public email they can't be contacted.

You can also bulk-export discovery results to CSV and mark them as contacted in one action.