I did some shopping for fans and battery packs, and found good, inexpensive case fans from Newegg and battery cases with built-in on/off switches.
Battery pack with on/off switch:
http://www.amazon.com/gp/product/B008SO6XXS/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
Fan:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835150054
![fan and battery pack]( "fan and battery pack")
The pack is a pretty awesome find because it has a cover to hold in the batteries and there's no need to wire a switch separately.
Battery pack with on/off switch:
http://www.amazon.com/gp/product/B008SO6XXS/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
Fan:
http://www.newegg.com/Product/Product.aspx?Item=N82E16835150054
The pack is a pretty awesome find because it has a cover to hold in the batteries and there's no need to wire a switch separately.