Coolerguys PRO-Metal Cabcool1201-M Lite Single 120mm Cooling Kit for Cabinet & Home Theaters
They are high quality dual ball bearing fans so running 24/7/365 they will last many years, not to mention we made them ultra quiet so you won't even be able to tell that they are running.
This kit comes with a wall wart style 2 prong AC adapter (110-240v) so you can power it from a standard wall socket or any device that has an AC output, it will work anywhere internationally if you adapt the plug. Along with the power supply is a single ultra quiet and reliable 5v 120mm Coolerguys fan, bracket, grills and all the screws, nuts, and bolts necessary to assemble and install the unit, completed size is (6.25" x 6.25" x 1.25")
The assembled kit can be mounted on any side of a cabinet, where room permits, by cutting a hole approximately 3/4" smaller on all sides of the outside bracket.
Fan(s) can be set to blow into or out of the cabinet depending on your needs, there are arrows on the fan showing which direction the air blows so you just need to face it in whichever direction you want (in our testing using a single fan works best as an exhaust over an intake but feel free to try it both ways and find what works best for your application)

The kit includes the following:
(1) Coolerguys Ultra Quiet 120x120x25mm 5 Volt Fan with 4pin molex pass through connector
(1) 110v AC to 5v DC power Supply with 4 Pin Molex (500mA)
(1) Black powder Coated Metal Fan bracket (6.25" x 6.25" x .125")
(1) Black 120mm Mesh Grill with Honeycomb holes
(1) Black 120mm fan grill
(4) Fan nuts and bolts
Pack - 4" Nylon Multi-Purpose Tie Black
All necessary screws, cables, and fasteners to complete the unit are included
Completed dimensions: (6.25" x 6.25" x 1.25")
Fan Specifications: Dimensions 120x120x25mm, Tail 24 inches, RPM: 1200, Air Volume: 45.2 CFM,dB: 19.7 Bearing: Dual Ball Life Hours: 50,000 @ 40C