you might want to look at getting a universal adapter at radioshack or somewhere like that. You can change the voltage on the adapter using dip switches and also it has several plugs that can be changed out to fit whatever device you are using. Just make sure that the voltage on the universal adapter matches the input voltage for the minibox, becasue if you keep it too high, you can fry the box. Not sure if this will work, but it is worth a shot? Or, you can probably call Insight and ask them for a replacement adapter.
My mother went and got a power adapter for it from the Insight store a while ago. It was the wrong one though. When she came back with the wrong one, I gave her the voltage and amp of one that we are using. So, we should have the right one later in the day.