you could parent it with an empty, and the empty has several options for display of the empty now.
use one of those … or use the ‘image’ option and attach a ready made one or make one in your favorite paint editor Gimp.
I used a camera lens icon and attached it to the front of the camera to overcome the parallax error
in the default Blender camera. (there are times it is hard to discern which direction it is pointing)
and to dress it up i painted on a green LED next to lens to indicate it is ‘on’
This worked so well that even with camera in far distance the lens icon is very visible and my problem went away… though somehow a camera lens pointed at you with a visible LED is
more inttrusive than just a lens:eyebrowlift2:
BTW: the object Blender uses represents the view frustum and it changes proportional to lens, near, far and other settings in camera properties … this is more appropriate behavior IMO