I found a power unit somewhere and i ripped it apart for it’s mesh housing and i cut a square out that was 130mm by 130mm.

I then crew out a hole on the inside side panel of my case that was 120mm round and that used a dremel tool to cut out the hole. Very carefully i cut and afterwards sanded down the edge to get rid of the excess plastic. I then used hot glue to adhere the mesh to the plastic. After letting it set for a bit to let the glue dry, i then put a thin bead of hot glue around the edge to seal it up.

*that seal has been since taken off. It looked real bad*

Here are some shots of the side panel back in place. The computer is cooler now and the sound of the 120mm fan is not very noticeable.