I have no choice to parent them to any body part.  When I load the prop it is already part of the only human figure in the scene.  When the parent option is selected, that human figure is not in the tree.

Scene with Simon

Load Prop

It's shown as Simon - Prop

I cannot parent it to Simon's head because when i go to set parent, Simon isn't in the tree.

It's the same no matter what figure is loaded into the scene, even M3 for whom the prop was created.  There is no way to parent it to a part of the body.