/find <username> - outputs the server on which a player can be found (if they can be found, that is!). If found, you can click on the message to teleport to the relevant server.
find.find permission is required to use the command.
Tested with Velocity 4.1.0
THIS IS NOT A PAPER PLUGIN. THIS IS TO BE INSTALLED ONTO A VELOCITY PROXY ONLY
Simply drag the latest .jar file into the Velocity plugins folder.
Check out images on my website!