Darn. Well that one's out then. Does anyone have the 12" Powerbook keyboard to compare?
For reference, the width of the Duo is 10.9" = 277mm
That's probably not a dealbreaker.
So is the one in the Duo, isn't it? No hack necessary - at worst, some software key remapping.
A later keyboard might work (11" MBA?) with a Key Warrior ADB, and a tap into the ADB lines on the dock connector.