Caveat: Haven't tested, but it should work. If you take an invisible token , give control of it to the player in question and make sure that the aura is editable and set to an appropriate size, but that "players see aura" is checked OFF , they should be able to see (and move) that token. A player who does not have control (or editing) should not be able to see it. If you think the situation is going to come up, have a token completely prepared sitting somewhere on your map, but with no player controlling it. Then grab it and give control to the player in question, then place it on the location you want to pinpoint.
