The fridge fan came from a guy on Ebay that makes a kit for that purpose.
As I understand it, if you have a unit that is around 2007 or earlier, you can tap off the light. If you have a later model as I do, they rewired and you can no longer do it that way...So what I did is took a very small gauge wire and ran it down the drain tube. It is small enough that it should allow water to pass no problem. My load center is right below the fridge, so I routed the wire to it and used a free circuit. Now the fan has a dedicated fuse as well.
I have not used it on a trip yet, but I hear they work really well. It has to be better than one of those little battery operated fans.
Link -- http://cgi.ebay.com/ebaymotors/DOMET...Q5fAccessories