adding eyes meshes to a ready rigified how to connect the bone systems ?.

Well i got a a figure one object rigified, and textured etc.
And i made two eyes objects also textured with an inverse IK to follow an empty as eye focus point.
So now i have 3 objects, but also different bone systems.

How do i set the base of each eye fixed to the head bone of the rigify figure ?.
(as these are separated meshes and objects), i cant simply join the meshes as its allready textured