Hope you like the photo and idea of modifying for a fan. It's gruesome but effective. There are several Pi-FAN for sale but for some reason none of them, i found, have the CFM the ones from the acrylic case I bought from DIYzone store on ALIExpress. Been meaning to ask them if they sell just the fans he obtains. Other PI-FAN(Manufacture label), I have bought, are inferior and the CFM is less then the breath of a Kitten in a full slumber and about as quiet. 8-/ Maybe they just need to break in? https://www.aliexpress.com/item/32621151739.html
These acrylic cases need to be hot to the touch before assembly. Very stiff acrylic. They have powerful loud fans though!