Please can you add a player tracking plugin - my suggestion would be Simple Player Tracker.
At present the only plugin that could allow this sort of thing is Simple Compass however this only works as a tracking plugin if the applicable add-on is installed and since we can't upload .jar files we can't add the player tracker plugin to the trackers folder in the plugin files, making the plugin useless as a tracker.
Simple Player tracker: https://www.curseforge.com/minecraft/bukkit-plugins/simple-player-tracker
If it is possible for you to install add-ons for existing plugins then that would work too with the simple compass plugin.
Player Tracker for Simple Compass: https://github.com/arboriginal/SCT-PlayerTracker