Indicate with markers the direction of Gameobjects which are outside of the camerafield.

I have a scene with a big map on it. On this map there are several players on diffrent positions in the map area. My Camera renders just a part of the map and not all players can be seen by the user.

I want to create a UI overlay, wich indicates the direction of the players which are outside the camerafield.

I struggle to get these markers aligned on the bounds of the camera and in the right angle to the WorldPosition Center of the Camera View. The camera is in perspectivic mode.

I tried many diffrent ways and wasted a lot of time with it, but I dont figure out how I can get it work. I know that there is more than one solution and this solution could be not that easy. But I hope that someone can give me a approach or a way how I can get it work. Hope someone can help me :)