As far as location goes, Dragoneye Rune is basically an enhanced Arcane Mark that allows the caster to divine the direction and distance of the marked item 3/day. Get a couple of single-use magic items so that each of them to cast the spell on a ring or amulet worn by the other.
As a single casting of a 2nd level spell with a permanent effect, it's going to end up being much cheaper than a continuous magic item to get this particular effect.