The Ohio Resource Center has a wealth of information for teachers and parents. Here is a list of books suitable for grades K-2 that focus on characters that write.
Writing for Many Purposes: Characters That Write
The books in this bookshelf will help children begin thinking about how writing is important for many, many reasons. The books are organized by the type of writing depicted in the stories. The literacy links help teachers utilize these books to serve as introductions and models when discussing purposes of writing or when beginning instruction on a specific mode.