Well I am late to the party but the way I did it was too use old 2 wire NorthBridge South Bridge computer fans powered from the generic Cigars International Cigar Oasis optional extra fan power source. That power source uses ribbon power connectors that can go through the door and it sill will seal. The fans run 24/7 unless you use a timer though.
Its hard to find the 2 wire fans but CI sells them for a remarkable markup, still not bad really, over what the computer stores used to sell them for back in the day.
This is what I am talking about. You do not need the cigar oasis humidifier just the dc power supply.
http://www.cigarsinternational.com/p...-FANKIT&cat=10