If you for some unknown reason STILL are needing to get your rider a present (unless they already have one) to put under the tree, a super unique gift that I can bet none of your non horsey friends would never think of getting is a tail for your horse/pony that goes to the A shows.
These tails ( hair extensions) are real horse hair and come in an assortment of sizes and colors. Black with some brown mixed in is the least expensive, true black and grey/white being the most expensive color. Ideally go for the full pound of hair for a fuller look. I believe Ponies have a shorter version for obvious reasons. To protect your investment (it is that) get a Tail Bag which comes with a nylon sleeve. Also purchase a 4″ Ace Bandage to wrap the tail once it is braided in on your mount. The Camden Tack Shop will have everything that you need.
Care for your tail the same way you would care for your own hair; shampoo and condition your tail, using a leave in conditioner and making sure that when you return it to its bag it is completely dry first. Most times that requires you to take it home to air dry after a show but REMEMBER to bring it back to put back in your show trunk for the next time!