Is the in dash gps cover assembly a separate piece?

I have an advent stereo/gps on my 2013 Camry that keeps getting stuck in calibration mode and killing the battery. I would like to replace it but it seems that the options are limited and expensive.

When I shop online for replacement I see that some come with the big plastic assembly that meshes with the dashboard. These are the expensive ones. I also see others that claim they are compatible with the 2013 Camry but only show it with the screen and metal casing.

My question is this: is this cover assembly a separate item or do I have to get a new stereo that comes with one? I already have two and if I can just remove the old stereo and cage from the back of the one I have now I would save a good chunk of cash. Is this possible? Thanks!