How to : Object size always same in render view even the camera zoom in or out

[system]

I have minimap camera pointing from the top and a diamond shape navigator locator parented inside FPS. The diamond was on the top of the FPS. This camera will follow the FPS (I have done)

PROBLEM :
when zoom out the minimap camera, the diamond look smaller and it’s hard for user to see where they are.

Bro, is that any clue to maintain the Diamond object size even zoom in or out?

Here, Zoom.js (attached inside minimap camera) :

var zoom : int = 0;

function OnGUI () {

if (GUI.RepeatButton (Rect (210, 10, 20, 20), "+")) {
	zoom++;// This code is executed when the Button is clicked
	camera.orthographic = true;
	camera.orthographicSize--;
	
}

if (GUI.RepeatButton (Rect (210, 160, 20, 20), "-")) {
	zoom--;// This code is executed when the Button is clicked
	camera.orthographic = true;
	camera.orthographicSize++;
	
}

}

Thanks 1st

[DaveA]

I would put that diamond in the GUI (DrawTexture), or use a second camera at a fixed distance/fov just for that.