Maybe I should change the title to "Please, don't buy your kid a costume from a party shop". Those costumes don't look good at all. The best option always is DIY! A good makeup might be the only thing your kid needs, like the little "Queen of Hearts" below. If you want the same effect of the picture don't use white makeup use white powder instead. If you costume is all about the outfit, use real items not "costume clothes" like the little "Chaplin" or the "Clockwork orange" below.
You can also grab some clothes from your own wardrobe to create a little scarecrow. The result is pretty cool.
Of course, the fox costume is a must! And they are pretty simple to create. Here you can find a tutorial.