There is the double mode of the PadMu: two A4 ereaders with a "double mode" case for 1837€. Not quite what you're asking at all, but the closest right now as fa

There is the double mode of the PadMu: two A4 ereaders with a "double mode" case for 1837€. Not quite what you're asking at all, but the closest right now as far as I know.