From what I know, you can find the brushes at specialty stores, amazon.com and their online store.
The price is more, but the quality is excellent. No hairs falling out, ever. The brush handles are really nice (glossy black) that are thicker than normal. But what I like the most is the cut of the brush and the hair. Most brushes are too 'flippy' as in the hair is cut too long for it to actually DO anything.. it just flips the product around. These are more compact and you actually get more hair in the casing.. it's thicker. So it picks up product better and applies easier. Also they have innovative cuts, like the pointed foundation brush (never saw that before) and such that for a pro like me, I squeal over... just different... Sign up for their newsletter for deals and such. They recently had a all pro set for $99 that I almost bought...