Go to the manybooks site and look at the genre section. There's a genre entitled "religion" which contains plenty of Christian fiction.
"The Lamplighter" by Maria S. Cummins can be found in the MobileRead ebook section. Just see the link at the top of this page. It may also be worth try Project Gutenberg as they may have a section for Christian fiction, all of which will be free.
Perhaps this will be useful:
https://wiki.mobileread.com/wiki/Free_eBooks