Cut it on a straight line up the middle of the back of the sack to the top.
Then cut a round shape spot for the neck.
Then use some paint, crayons, fabric or markers to decorate the paper bag.
Buy a bandana for the neck scarf or make your own scarf by cutting out a fabric.
Get enough fabric to fold your piece in to a triangle to tie around your cowboy fancy dress costume.

Let your child wear a denim pants and a white t-shirt to make your child look like a real cowboy.
Of course a cowboy is not a cowboy if he doesn’t have a gun or a horsewhip.
Try to have a toy gun or a toy horsewhip.

You could also buy him a cowboy hat that is found on the nearest kids fashion store.
This is very cheap and this will not cost you a lot of money.
Don’t forget to purchase your son a cowboy shoes to get even more authentic you can buy this at any cowboy fancy dress costume shop near your place.

And try to make a horse stick all you have to do is cut a old carton cut it into a horse head shaped and put it into the edge of a stick then add some design on it or even use your ability in drawing a horse face on it.

Having a unique cowboy fancy dress costume for your child doesn’t cost you a lot of money.
What you need to do is use your creativity and always remember that thought always counts and not the price of the item.