Princeton Art & Brush offers more than fine art professional brushes. They also offer a big handled kids' brush where the handle happens to be brightly colored, the hair happens to be natural, and the price happens to be affordable.
The bristles on Princeton's Stubby brushes - the kind in the Big Brush Bucket - are actually pretty coarse and rugged. They work well to move around thick and messy paints like acrylic or tempera - or for adult encuastic artists since the natural hair doesn't melt in the wax.
Princeton's Good Camel Hair brush is a basic watercolor brush used for kids' art and craft projects, similar to the brush you might find in an 8 color watercolor oval pan set, but a little better. It comes in more sizes too, 10 round sizes in all, up to a nice sized #12.