A striper brush usually comes with the nail art brush sets (read my review on Born-pretty-store nail art brush set)
But if you are not satisfied with that brush you can get 3pcs striper brush set where you will get striper brushes with 3 lengths.
Here's a close up pic to see the different lengths
As you can see, the red striper brush is really short
The blue brush is a little longer
And the green brush is the longest.
Just as I got the brushes, I wanted to give them a try, so this is the nail art I did using the brushes
But It's kinda toooo boring.
So if you want to buy the brushes, this is the link-
And you can get it for even smaller price by using this coupon code
to get 10% off when you buy something