Did C.S. Lewis ever write (or authorise) any other works that are canonicaly set in the Chronicles of Narnia universe?
To clarify, I'm asking about works (of any length) besides for the main seven books.
On Wikipedia's page for C. S. Lewis, on there no mention of any other works set in the Narnia world, though there are some works which were never finished. Likewise, on their Chronicles of Narnia page, there is no mention of any other works besides for the seven novels.
However, his estate has authorized at least three other books:
While it doesn't look like C.S. Lewis ever did himself, his estate has authorized at least one other book, The Giant Surprise: A Narnia Story, by Hiawyn Oram.
C.S. Lewis never published other Narnia related books. Chronicles consist of 7 books but there were side works of the Chronicles from his publisher and his stepson.
Also there was The Giant Surprise: A Narnia Story, but it was not written by Lewis. He supported the work.
The only other Narnia fragment available, as far as I know, is an early draft of the first chapter of "The Magician's Nephew", quoted in full in Walter Hooper's "Past Watchful Dragons". Diggory and Polly are both in this section. Trees can feel pain (some can, at least) and Diggory has the power to understand animal language. Mrs Lefay also features briefly and appears to be a good witch.