How can i search a gameobject and access its script?

I try to create a prefab for coins. If i use “public PlayerStatManager playermanager;” I have to drag the PlayerStatManager manually in the inspector every time i put down an another coin. Is there any method that automaticly search the PlayerStatManager?

using UnityEngine;
using System.Collections;

public class Coin : MonoBehaviour
{
    public PlayerStatManager playermanager;
    public float rotateSpeed= 2; 
    public float value= 100;

    void Update()
    {
        transform.Rotate(Time.deltaTime, rotateSpeed, 0);
    }

    void OnTriggerEnter(Collider other)
    {
        if (other.gameObject.tag == "Pickuprange")
        {
            playermanager.Score = playermanager.Score + value;
            Destroy(gameObject);
        }
    }
}

PlayerStatManager playermanager;

void Start() {
playermanager = GameObject.FindWithTag("Manager").GetComponent<PlayerStatManager>();
}

this gets the playermanager that is currently on the gameobject tagged as Manager.
make an empty gameobject and tag it as Manager, put the PlayerStatManager script on it.
This script will reference it and automaticly set it.