I have been using old cell phone chargers and plug in AC->DC power sources for the last year or so to power the 12v fan in my incubator. Worked great with one 120mm fan, but the latest bator is a converted full size frige and looked like two 120mm fans would be required to distribute the heat more evenly. One of the cell phone chargers was really struggling running two fans, so I pulled this old handy AC->DC power source out that I have had for years to give it a try.

WAY BETTER!!