I made it from Liberty prints, both still available in the shop (Phoebe, the small scale floral, is here, and Willow, the circles, is here). You can easily get one side of the hat out of a fat quarter (two fat eighths), even for the larger sizes.
I actually intended the Phoebe print to be the outside and Willow to be the inside, but I've rethought since making it - Phoebe is a print that seems designed to be seen in tiny peeps of the inside!
Since Liberty is so fine, I interlined the hat with white quilting cotton (ie cut the pattern pieces out of white cotton, placed it against the wrong side of one of the Liberty prints, and henceforth treated it as one piece of fabric) as well as adding interfacing to the brim as per the book's instructions.
This hat is actually too big for my teeny weeny little baby, but it's so entertaining putting it on her and watching it slowly slip down we're making her wear it anyway. Have I mentioned what a superb mother I am? I keep looking for the tiny baby hat I made for Jasper (at the bottom of this post), but it appears to have been eaten by one of our many house moves. Maybe I'll make another. Or maybe I'll just continue to be amused by my tiny headed baby and her giant sunhat...