Most people who have an OpenPGP key upload their public key to one of the on-line key-servers. These key-servers sync keys with each other, so you can find any

Most people who have an OpenPGP key upload their public key to one of the on-line key-servers. These key-servers sync keys with each other, so you can find any published public key from any one of them. Try https://pgp.mit.edu/ https://pgp.mit.edu/ for instance. Enigmail in Thunderbird offers a way to search these key-server from within the mail application, perhaps Mailvelope has this feature as well?