How do you show a monitor's contents on a texture in a Unity Scene?

I am trying to create a flat surface in a Unity scene that will show the contents of the user’s main desktop monitor while they are in VR, so that they do not need to take their headset off to access their main monitor. However, I am stumped as to how to go about doing this.

The scene will only display on the headset and will not be mirrored to the desktop so before you ask, no, you wouldn’t end up seeing this.

I understand I might need to use a Render Texture to go about achieving what I am going for, but Render Textures only seem to take input from an in-game camera. I need the texture to show whatever is being shown on a certain monitor outside of the game. I’ll do a quick photoshop edit of that screenshot (from Garry’s Mod) that I linked before, to help explain what I am going for:

I’m having trouble finding any way of doing this via Google or via searching for posts on the Unity forums.

Does anyone with knowledge about VR development with Unity know a way of achieving this?

Future Googler’s looking for a solution who just want to capture desktop without the clutter of outdated VR stuff: here’s a much simpler package based on the same Windows Capture plugin that is just the capture stuff that isn’t buried in HTC stuff.