The gizmo appears where the object root is. So with third party objects that have their root at a different location, you will have that issue. To fix it:
Select the object in your scene.
scroll down a bit in the modify panel to the "Pivot" section.
Use the quick set box to set the root (pivot) to the lower center of your object.

See the manual page for more in-depth information:
https://manual.reallusion.com/iClone-8/Content/ENU/8.0/30-Set/Prop/Pivot_of_Prop.htm