Transparency sorting using separate camera

I have a simulated 2D game with a lot of parallax planes that differ in depth that I'm rendering using a perspective camera. I'm sorting these planes orthogonally so the position of the camera doesn't matter, and everything works fine. What I need now is to be able to rotate the camera to a certain degree. However, when I'm not looking straight ahead the transparency sorting no longer works. What I need is for the camera to always sort the transparent planes orthogonally along the Z axis, even if the camera is slightly rotated along the Y axis. Is there anyway to do this in Unity?

The only thing I've found so far is by manually setting the render queue on each plane's material, but that solution does not work in this case. There are far too many planes in the scenes and a lot of the planes share materials with eachother. It would literally take weeks to reorganize everything that way and I do not have that time.

I hope there is a simple solution to this problem, since the technical solution is really simple, I just haven't found a way to do this in Unity.