Ok go to radio shack and buy two 12VOLT DC computer fans that have only a red and blue wire coming out of them. (do not buy the ones with the led lights on them) Then go to walmart and buy two 120V to 12V DC wall adapters. Stip the wires on both the adapter and the fans. On the adapter there will be a wire that has a dotted white line or a solid white line (this wire is the hot wire). The other wire on the adapter will be mostly black with some really small writing on it (this is the negative wire). Now solder the red wire from the fan to the hot wire on the adapter. Then solder the blue wire from the fan to the negative wire from the adapter. That is it just plug them in to make sure they work then place a fan pionting down on the top to one side of the incubator and the other one on the bottom facing up on the other side to rotate the air.
If your adapter is a varaible volt adapter make sure it is set to 12V DC. And make sure you tape up the connections so you don't get shocked. There's nothing to it, good luck.