I used 5 volt fans because I was plugging them into a USB port. There are 12 volt versions, too. I think this is what I used, but they're NLA: https://www.amazon.com/gp/product/B016U7EF6Q/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 At lease this will give you an idea of the dimensions of the fans. There are many others to choose from on Amazon.