PlaceCenterAtOrigin.cs

using UnityEditor;
using UnityEngine;

public class PlaceCenterAtOrigin : MonoBehaviour {

    [MenuItem("GameObject/Place Center at Origin")]
    static void PivotFixer() {
        Transform child = Selection.activeTransform;
        //Vector3 diff = child.rigidbody.worldCenterOfMass
        Rigidbody tempRB = child.gameObject.AddComponent<Rigidbody>();
        MeshCollider tempMC = child.gameObject.AddComponent<MeshCollider>();

        child.position = Vector3.zero;
        child.position = -child.rigidbody.worldCenterOfMass;

        if (child.parent) {
            child.position += child.parent.position;
        }

        DestroyImmediate(tempRB);
        DestroyImmediate(tempMC);
    }
}