I found original file on indiegogo for printing your own back case panel to suit the 3rd cooling mod see files (back case) and (SSD lid). I added extra vent holes for diy 3rd cooling mod my remix (back mod more vent holes) havent tested but lines up with cutouts on 7y30 shroud.

shrouds to suit you processer Stl files for back panel and ssd lid found Herr https://www.indiegogo.com/projects/gpd-win2-third-cooling-mod--2#/

shroud stl files and diy write up found here all credit to the person that posted this. https://bitbuilt.net/forums/index.php?threads/gpd-win-2-custom-heatsink.3535/