Take a look at NoteShelf ($4.99, USD). Now, I'm not left-handed, so take what I say with that in mind...
But, the wrist protection part is the full page. As you mark on the page, the protection moves down. Plus, there's a zoom function that only highlights a certain area for writing (the rest below the input area is again, the whole screen. It'll automatically move forward as you get to the end of the line. Plus, the zoom function has buttons that can be switch to the left side of the window so they'll be out of your way.
It's quite a nice little hand-writing app. My favorite, at the moment, though of course, YMMV.
Good luck in your search.
Marilyn