camera RotateAround, limit angles.

hi, I am working on a app with a globe, I need to navigate the globe by dragging it google maps style.

That part I have working by using this method : Link

Now my problem is when navigating it, the camera gets rotated in some directions that makes look like the globe is turned upside down etc. I want to limit my globe (the camera) to always be the right direction (north up, south down). Also I want to be able to limit how high/low, the user can navigate the globe. No need to be able to see straight down/up at the poles.
All help and hints appreciated :-)
Thanks, Per

Something like this, orange area being the allowed area:

my code so far :

 private void HandleDrag(Vector3 touchPosition)
     {
         _currentTouchPos = getTouchHit(touchPosition);
         RotateCamera((Vector3)_touchStartPos, (Vector3)_currentTouchPos);
     }
 
     private void RotateCamera(Vector3 dragStartPosition, Vector3 dragEndPosition)
     {
         // in case the spehre model is not a perfect sphere..
         dragEndPosition = dragEndPosition.normalized * SphereRadius;
         dragStartPosition = dragStartPosition.normalized * SphereRadius;
         // calc a vertical vector to rotate around..
         var cross = Vector3.Cross(dragEndPosition, dragStartPosition);          
         // calc the angle for the rotation..
         var angle = Vector3.SignedAngle(dragEndPosition, dragStartPosition, cross);
           // roatate around the vector..
          Camera.main.transform.RotateAround(transform.position, cross, angle);
        }
 
     private Vector3? getTouchHit(Vector3 checkPosition)
     {
         RaycastHit hit;
         if (Physics.Raycast(Camera.main.ScreenPointToRay(checkPosition),out hit))
         {
             return hit.point;
         }
         return null;
     }