Place object in line with camera and other object

In my game I have an object which is far away and for certain reasons I do not want to render that object. The object does not really matter but the player still needs to know where it is. What I want to do is, say the original object is 5000 units away, I want to make a sprite or an object that is in line with the player and the original object which will be closer, maybe just a few units away from the player. This diagram I made kind of represents what I am trying to do. The green dot is the camera, or player, and the blue line is where I want to place the new object in line with the original object which is the grey dot. The red of course is just the line that all of the objects are on.

Placing an object between 2 objects is a simple vector3 operation, something like this:

blue.position = green.position + (grey.position - green.position) / 10f;

As an alternative, why not using a canvas? That way, you can be sure that it is always rendering over and at the same distance of the camera; The camera got functions to know the position of world gameobjects on the screen, something like this:

public Image canvasImage;
public void Update(){
   canvasImage.transform.position = Camera.main.WorldToScreenPoint(grey.position);