The case I use is a mixer case for professional use (which... err... makes the thing not really cheap) and because it is designed to withstand shocks and heavy weights it is perfect to protect the components. It has the perfect size as well - everything fits as if the case would have been especially designed for yume =)
It has a weight of 5kg which, with the additional weight of 2.5kg that yume has, yields 7.5kg. Okay, it's not THAT light but I think its light enough since I won't take it with me everyday.
The most important criteria that the case had to fulfill was a cover which I can put over the controls because I didn't want to destroy the display when bumping the case on something sharp.
Another important criteria was that the case had to provide a possibility to mount a front plate where the controls can be mounted on. The mixer case has two rows with variable mounting holes (for 19" mixers), so it's also perfect in this way.
The case can be ordered at MG Elektronik located in Koblenz (Germany) and you should be able to see somewhat more detailed specs here.