Great idea and gift!  I'm not sure where to find 
decorated cel books, either.  If you can't find 
one, perhaps you could decorate one.  I decorate 
notebooks and folders by sticking stickers, 
glueing pictures/photos/comic strips/etc on them, 
and putting clear contact paper over the pictures 
to preserve them. Depending on the project, I'll 
use one sheet of contact paper for the entire 
cover or cut the contact just a bit bigger than 
each picture as a clear frame.  I've never tried 
it on a cel book, though.  
Good luck! 

J