how to duplicate a button via script?

I have the following code:

public GameObject characterButtonPrefab;
public GameObject characterButtonContainer;
public GameObject optionsContainer;

public GameObject[] charButtons;
private int charButtonsIndex = 0;
private Text[] cBT;
private string[] buttonTexts = new string[] {"Strength 5", "Agility 5", "Intelligence 5", "Charisma 5", "Diplomacy 5" };

private void Start()
{
    LevelIsOver = false;
    IsNextWave = false;
    //Time.timeScale = 1;

    for (int i = 0; i < charButtons.Length; i++)
    {
        int size = charButtons.Length;
        cBT = new Text[size];
        GameObject container = (GameObject)Instantiate(characterButtonPrefab);
        container.transform.SetParent(characterButtonContainer.transform, false);
        cBT[i] = characterButtonPrefab.transform.FindChild("Text").GetComponent<Text>();
        cBT[i].text = buttonTexts[Random.Range(0, buttonTexts.Length)];
        charButtonsIndex++;
    }

    //if (charButtons.Length > 0)
    //{
    //    GameObject currentChar = (GameObject)Instantiate(characterButtonPrefab);
    //    currentChar.transform.SetParent(optionsContainer.transform, false);
    //    currentChar.transform.SetSiblingIndex(0);
    //    currentChar.GetComponent<Button>().onClick.AddListener(() => CharacterSelection());
    //}
}

I declared the size of array to 20 in the inspector and everything work fine. The buttons are created and text changed. The question is how do I duplicate the first button in that array to another panel ? I have searched the internet but nothing found about this.

I have tried this:

GameObject currentChar = (GameObject)Instantiate(charButtons[0]);
     currentChar.transform.SetParent(optionsContainer.transform, false);
     currentChar.transform.SetSiblingIndex(0);
     currentChar.GetComponent<Button>().onClick.AddListener(() => CharacterSelection());
 }

But I get ArgumentException: The Object you want to instantiate is null.