Here is a good touch panel: http://www.ebay.com/itm/10-4-U.....3cbacdff6c
You could use something like that for the touch interface. Also, the fancy clipboards that have space for a notebook inside would make a great case.
The hardest part will be finding the right screen. Usb only screens can be fairly high latency and expensive, and it might be kind of difficult to find a separate screen that is compatible without extra chips.