Probably not a hot pick, but I would check the Aozora Bunko books: Here, Have a List of Aozora Books by WK Level
The children’s books are N4 with a bit of N3 usually. The downside (but perhaps an upside for you?) is that they use hardly any kanji.
Just be aware that many of the books are old and some use old kana orthography, but that will be indicated in the book’s details (新字新仮名).
EDIT:
Corrected the kanji for old orthography. 新仮名 indicates only new kana, but the full entry in Aozora is 新字新仮名, because it covers both kana and kanji.