First off, Welcome to AquariumAdvice.com
I've never run a nano myself (but have been curiously investigating the possabilities of one for my office at work) I would imagine it wouldn't be too dificult to retro fit a PC
fixture to fit over a nano-cube. You might want to check out our DIY
section, lots of talk in there about retro-fitting lights and making cutom hoods. I also know there are a number of sites out there devoted specifically to nano-tanks.