I like mine because it has a concaved side where the bristles are set inward. These are for getting under the nails' free edge and removing debris.
You can get a nail brush at any drugstore or mass merchandiser. I got this one (I have two, actually) from a manicure company that did at-home parties. I googled and couldn't find anything about them. Lucky for me, these brushes have held up and still work wonderfully.
Do you use a nail brush on a regular basis?