Hello All,
I am quite interested in this project and excited to see what comes of it! I came across this:
https://www.olimex.com/Products/DIY%20Laptop/
the other day and feel like it might be an option to consider. I also think that that the Novena case would be a good option as well for a small portable (obviously not really a laptop in the general sense) PPC machine.
Of course it all depends on how far down the design path you are :).
Olimex could be a good choice. However, it's ARM based, not PPC. But since it's open source hardware
AND Olimex has a LOT of experience as a manufacturer of Arduino and other boards, it would be interesting to at least talk to them.
AFAIK, this case was also on the list. But because of the dimensions it fails.