Need an STL file creating for 3D Printing

Hi

I need a part designing to fix to another 3d printed part (I have the stl file for the other part) -https://www.dropbox.com/scl/fi/1nth8igkp3i3bg7mafwht/mac-mini-m4-19-inch-rack-mount-hex-nut.stl?rlkey=uapt2pwhrz0am4qrnq5zxm9rh&st=rf9exu0x&dl=0

The bit I need creating is to hold a motu m4 audio interface - https://www.google.com/search?client=safari&rls=en&q=motu+m4+audio+interface&ie=UTF-8&oe=UTF-8
I have callipers so could provide the measurements of the device, - you will see a jpg attached, although this is not what I want, you'll see the a holder that was created to hold the device under a desk, this gives you a clue as to the curved sides. Also attached is a rough line drawing of what I want

for context when the 2 parts are joined together they site in 19"rack case with standard rack mount ears - the height of the unit is 2U, the the part to be created is about half the 19" width

Anywuestinos fireaway. The part is to be printed in PETG