Warm beer is foamy beer, and as wonderful as a kegerator is, the tower of the kegerator still introduces heat and heat leads to foam.  There's lots of frankly cheap and clunky keg tower fan options out there that don't work well, fit weird or fall short of being worth the money.  This setup is the same setup I use on my kegerator in my garage bar.  It's clicked along for years without issue and I have no doubt it'll serve you well too. 
 
The Bourboneur Keg Tower Cooling fan uses 80% less energy and moves 1.5-3 times the air volume compared to the same ordinary fans (2,200 RPM producing 38.5 CFM of airflow).  Long life dual ball bearings mean this workhorse will keep humming for the long haul. 
 
Package includes:
Keg Tower Fan
Mounting screws and Double sided tap based on install preference
1 US Plug Power Cord (approximately 5 feet)
3 foot length of air flow tubing