This isn't absolutely perfect but it is close. You can use this on your Waveshare Gamehat without any modification to the hat itself. I used the original screws that came with it on the back but internally I had to use 6 M3 1/4" or 5mm standoffs. I chose to drill the holes for the standoffs by hand with a 3/32 bit instead of adding them to the print. You will notice a 5mm gap between the screen and the screen bezel. That is an attempt to allow better airflow, an RP3b+ gets pretty hot. The joystick shortens the throw of that giant stock one to about half of what it was. All the design was done in Tinkercad so you can customize it or change it to your liking. https://www.tinkercad.com/things/fIJKFJLqyn2

Have fun and if you love it, please let me know!