Need help with Brushes!!!

Does anybody know where I can get a brush/brushes that are just circular, but are darker on one side and then fade as they go across to the other side of the brush? There'd have to be at least four of them, one of them with the darkest part on bottom, one with it on the top, etc...Hope you guys understand what I mean. Anyone know where I can get brushes like that?

 

Have you tried the deviant art place yet? If so then try making some theyre not very hard to make.