Synced position with two cameras?

I have two Ortho cameras.

One has (0,0,0) rotation and it shows the background of the scene, along with the movement grid, which is depicted in a faux isometric view (meaning, the isometry is painted on, it doesn't come from the camera's angle itself). All elements shown by this camera are 2D.

Now I have another camera, with a isometric rotation (30,45,0), which shows my character 3D models in a real isometric projection.

The issue I am having is how to sync the positions of these two views, so when a character is moved to a grid cell position, it appears in the correct place (right now it's all over the place, because of the rotation).

Any help would be great, cheers