ExtendedHitZone.cs

using UnityEngine;
using UnityEngine.UI;
using UnityEngine.EventSystems;

public class ExtendedHitZone : MonoBehaviour
{
    [SerializeField] float extraWidth = 50;
    [SerializeField] float extraHeight = 50;

    public class EmptyGraphic : Graphic
    {
        protected override void OnPopulateMesh(VertexHelper vertexHelper)
        {
            vertexHelper.Clear();
        }
    }

    void Awake()
    {
        CreateHitZone();
    }

    private void CreateHitZone()
    {
        RectTransform rectTransform = GetComponent<RectTransform>();

        GameObject hitZone = new GameObject(name + " Hit Zone");
        RectTransform hitzoneRectTransform = hitZone.AddComponent<RectTransform>();
        hitzoneRectTransform.SetParent(transform);
        hitzoneRectTransform.localPosition = Vector3.zero;
        hitzoneRectTransform.localScale = Vector3.one;
        hitzoneRectTransform.sizeDelta = new Vector2(rectTransform.rect.width + extraWidth, rectTransform.rect.height + extraHeight);

        // Create transparent graphic
        hitZone.AddComponent<EmptyGraphic>();

        // Delegate events
        EventTrigger eventTrigger = hitZone.AddComponent<EventTrigger>();

        // Pointer Up
        AddEventTriggerListener
        (
            eventTrigger, 
            EventTriggerType.PointerDown,
            (BaseEventData eventData) => 
            {
                ExecuteEvents.Execute(base.gameObject, eventData, ExecuteEvents.pointerDownHandler);
            }
        );

        // Pointer Down
        AddEventTriggerListener
        (
            eventTrigger, 
            EventTriggerType.PointerUp,
            (BaseEventData eventData) => 
            {
                ExecuteEvents.Execute(base.gameObject, eventData, ExecuteEvents.pointerUpHandler);
            }
        );

        // Pointer Click
        AddEventTriggerListener
        (
            eventTrigger, 
            EventTriggerType.PointerClick,
            (BaseEventData eventData) => 
            {
                ExecuteEvents.Execute(base.gameObject, eventData, ExecuteEvents.pointerClickHandler);
            }
        );
    }

    private void AddEventTriggerListener(EventTrigger trigger, EventTriggerType eventType, System.Action<BaseEventData> method)
    {
        EventTrigger.Entry entry = new EventTrigger.Entry();

        entry.eventID = eventType;
        entry.callback = new EventTrigger.TriggerEvent();
        entry.callback.AddListener(new UnityEngine.Events.UnityAction<BaseEventData>(method));

        trigger.triggers.Add(entry);
    }
}