WARNING: when you wire in the fan, do NOT use the normal controllable fan port. Use the Hotend port which is always on. Using a controllable port + Buckconverter can blow the microfuse on your board. I have a picture that shows which port to use.

Remix of another cover, but made for a bigger fan 80x80x25 since they are more silent than the slim fan.
I also added room for a buck converter to get the 24v down to 12v for more fan choices.

This will require you to raise the printer.

I made these legs for my Ender 3 v2.
https://makerworld.com/en/models/473595

I also made a fan board for the PSU, can be found here:
https://makerworld.com/en/models/473581

Buck Converter is the LM2596 Display:
https://www.aliexpress.com/item/4001202088404.html

The fan I used was the Arctic F8:
https://www.amazon.com/ARCTIC-Silent-Ultra-Quiet-inaudible-Configuration/dp/B0119SLG18/

If you want, you can skip the converter and go for a 24v fan. This one I tried and is not bad considering the price. Still much more quiet than the stock
https://www.aliexpress.com/item/32967912432.html

but any 80x80x25 will work :)