GeorgeKS

Hi
It's tinkering time.
I recommend you use a small file tool (for the finishing) along with a rasp (for the rough work).
It's something most PC enthusiasts have done time and again.

Just make sure you do it away from your system, anfd wipe the I/O shield carefully to remove any lose metal powder.

Of course, you can always check from the manufacturer of your system if they sell them.