Well, you could borrow an iLiad, transfer the book to PDF there, then have the author sign the book using the iLiad's pen, re-merge the PDF... but of course, you can't do that (even if you know someone with an iLiad), because if it's a book you're likely to meet the author of, it's probably locked into DRM.
(Unless it's from Baen.)
The peel-off PDA protector idea sounds best to me, I guess. Then you could scan it in and add it to the reader.