As it's a cover I made this a snug fit, so don't 100% fill it or there won't be any give. I think technically this is my first design from scratch, so be kind..
Edit it online https://www.tinkercad.com/things/ezZNxabq8Se
Printer:
CTC 3D Printer
Rafts:
No
Supports:
No
Resolution:
0.1mm
Infill:
40%