They are an old set - a couple of years old now technically so that really does limit where you will be able to buy them off the shelf brand new. As others have mentioned you may manage to find a retailer with old stock [smaller independent toy shops with slower and lower footfall are your best chance] if they simply never sold out of the item.
Ebay is over priced on them at the moment although more will come on the second hand market given time but perhaps too much time in order to keep your little girl happy
![Smile :)](https://mlparena.com/Smileys/default/smile_001.gif)
The price is high because to be fair the exclusive pony it comes with is pricey in herself when being sold loose.
Therefore as long as you are prepared for potential shipping costs, perhaps you could post over in the Wanted forum as being on the look out for this set and hopefully someone will be able to help you out.
Good luck! I hope you manage to track it down soon!