Thermaltake Mobile Fan AF0007 12CM External USB Cooling Fan for $16.49. Shipping is free on orders over $25. If needed, use this Filler Tool to pad the order to qualify for free shipping. Here is a screenshot for your reference. It has adjustable speed and can be used for cooling laptops, desktops, cabinet, and more. It also comes with an one-touch retractable USB power cable box. Most places have it for about $24.