PP is correct that libraries are not equipped for the most beginner-level of readers.
Look for the book series called, "Rime to Read: A Program For Beginning Readers." MCPL has it. Also, there are a number of Bob Books on the market now. Make sure to get the beginning level set for your child.
Books that have limited letter patterns (what you described) are called decodable books. As the child learns more letter patterns, they read books that include the new patterns. This web page has many good decodable book series listed.
https://www.thereadingleague.org/decodable-text-sources/