There are quite a few notebook stands out there like the one you mentioned (a lot of them better actually). They are meant for DJ - tabletop purposes. Not sure if they will fit onto a keyboard stand.
The problem is that most keyboard stands are not 100% sturdy. When you play hard, the stand will shake. There's always the danger of your notebook falling off, unless there's a way to secure the notebook on the notebook stand by screws. Notebooks are pretty light, so danger is there. Even then, excessive jerky movements may harm your notebook (particularly the HD).
They are notebook stands that fits on music stand. Suggestion is to keep the notebook on a separate stand (usually music stand with notebook stand adaptor) from the keyboard stand - for safety.