The database of licenses is public through the the ULS [0], and ae7q [1] has a bunch of archives and information about how to use that and provides tools itself that I used when finding a vanity.

-K5ETC

[0] https://www.fcc.gov/wireless/universal-licensing-system

[1] https://www.ae7q.com/query/stat/DataBase.php?SCHEMA=Lic