That's where Scholastic's Listen and Read can help. This site offers 54 read-aloud nonfiction texts for young readers, organized into eight different categories (see subjects below).
At the end of the text, a short list of vocabulary words appears. Students can listen to those words again, which should enhance vocabulary and comprehension. Like the main text, the voice for the vocabulary is a child's voice.
If you use this site with your students, I'd love to hear how it went!
For more informational text sources, try this page.