Using the new /player/search/{partial} endpoint, you can query matching players by 'prefix'.
The prefix must be between 4 and 15 (inclusive) alphanumeric or space characters. The returned array is at most 10 items. Where possible, active players are prioritized in the search results.
As with all API methods, this comes with no (long term) availability assurances.
Try it out and find more on the API documentation page.