Best fan for studio xps 8100

Hi, I am just looking a good cooling Fan that will fit my Xps 8100, just want a good one for when I am gaming to keep my temps down but I am new at this and don't want to buy a fan that wont fit.

Thnx

* Dimensions & Weight

Height: 16.1" (40.9 cm)
Width: 7.3" (18.5 cm)
Depth:17.9" (454.67mm)
Weight: about 22.4 lbs (10.18 kg)