In a previous post I gave a detailed description about how to build a ringflash adapter:
Few days ago I received my new flash for my mirrorless camera (NEX-5). The small flash came with this camera was very weak, but this new one has a guide number of 20, which is enough for most of the macro work. I've accommodated the end fitting to attach it to the new flash:
Minor modification was to add few fibers to direct the focus assist light to the ring for easier focusing also in the dark.
You can see a branch of fibers just below the sony sign. The new flash could feed many more fibers but I was lazy to rebuild it again.