You can buy the pattern here.
Twilight Pony Hat
There is a typo in the pattern but only when referring to the colors when making the eyes. Instead of saying "darker purple" it says "dark pink". I will fix the PDF pattern as soon as I can.
There are some tricks to attaching the mane. When sewing on the front mane, make sure you tack it down around the ears in both the front and the back. I even tacked it down on parts of the horn. This will prevent the mane from flopping in front of the eyes. It also makes the slit fit around the horn better.
When attaching the back mane, make sure you wrap it around the hat and tack it down on the side, otherwise it will flop down behind the hat and won't be seen from the front. Line the mane up with the back edge of the front mane. I actually stitched into the bottom edge of the front mane to ensure there weren't any gaps when the hat was being worn. You might want to make a few stitches in the middle of the back mane or pin it down to keep it from bunching up as you sew around the edges.
The horn is pretty long. If you prefer a shorter horn, you can always do fewer rows.I hope you enjoy the pattern. I have appreciated all of your feedback. I feel that it has helped me improve my skills. Please feel free to contact me with any questions you might have. yarneemarmee@gmail.com .
Happy Crochet!