I bought a clone 7 inch PanelDue from Fysetc on AliExpress. Frustratingly, the vertical separation between the mounting screws on this clone is 102mm rather than 98mm, so it doesn't fit in the standard cases. So I made my own, as well as a bracket to fit to the 15x15mm extrusion on the Railcore II.

The bracket mounts to a 50mm square hole pattern on the back, so it is compatible with some of the other panel due case mounting brackets already out there.

4 M3 x ~16mm screws hold the case together
4 M3 nuts are needed for mounting the bracket

My bracket bolts to the top extrusion of the Railcore II and tilts the display back by 10 degrees to make it a little easier to access.

There are two places you can thread the cable out of the back, and some vent holes.

The SD card and USB socket are accessible directly. The two buttons on the controller can be pressed with a straightened paper clip or similar.

I put a pattern on the front surface, which is suitable for 2 color printing by swapping the filament out a few layers into the print. The pattern can be edited or deleted in the Fusion 360 file.