Mater Amabilis schedules The Way of the Cross: A Story of Padre Pio and The Young Life of Saint Maria Faustina, both by Claire Jordan Mohan, to be read during the Easter season in Level 1A.
These are nice saint stories that focus on the youth of the saint while still telling a little of their adult lives. I read The Way of the Cross aloud to First Son in second grade (and First Daughter, who was five). We then discussed it a little rather than a straight narration. I thought we all enjoyed the book, though I know First Son doesn't remember much of Padre Pio. This book is ten chapters. Some of the chapters were a little long for First Son to follow and narrate well in second grade.
First Son read The Young Life of Saint Maria Faustina independently, then narrated it to me. First Son and First Daughter have sung the Divine Mercy chaplet in a children's choir for the past three years, so First Son could place those in context. St. Faustina is also one of my grandmother's favorite saints because they are both Polish. This book is eleven chapters. They seem like they might be a little longer than in The Way of the Cross, but they are also in a larger font. First Son seemed able to read and narrate them adequately in third grade.
Two years ago, when I was gathering materials for second grade, I had trouble finding The Way of the Cross. I finally found a copy on the website for a monastery (or something) in Canada. More recently, I found The Young Life of Maria Faustina used on Amazon for a reasonable price. There's no doubt that these out of print books are a little harder to find.
I think you could substitute another of Claire Jordan Mohan's biographies. I bought a copy of Katie, The Young Life of Mother Katharine Drexel when I purchased The Way of the Cross and will probably use it as a substitute in fourth grade for another out-of-print biography. Our library has two of her books: The Young Life of Pope John Paul II, which First Son read and enjoyed (not for lessons, just for fun), and St. Maximilian Kolbe: The Story of the Two Crowns. It seems like The Way of the Cross seems particularly hard to find, but some of the others are readily available used at reasonable prices.
Alternatively, I think a book from the Encounter the Saints series would be a good substitute. These are readily available, though it appears some of the individual books do go out of print and become harder to find. We have about ten of these books and have enjoyed them. First Son could probably have read one independently in second grade, though we may have broken some longer chapters up.
Another good option would be a book from the series being reprinted by Mary's Books, In the Footsteps of the Saints. We have a few of the Level 1 books, which First Son could have read independently in second grade. I don't have any Level 2 or Level 3 books (which are apparently available in some places already), but I talked with Linda at Sacred Heart Books and Gifts, who carried just about all of the available books in the series. She said the Level 3 books would be a bit easier than the Vision saint books, which are written at the fourth or fifth grade level. They would probably be wonderful substitutes and you could choose a saint dear to your child's heart or interests.