Well its fairly easy to create one in any modeller, just select some polys on the forehead, extract them out and shape to fit. They will have the same UVs as the head so you can apply the same texture.

EDIT : ehh why did my previous post disappear ??

Anyway i will post it again, basically i paint out the brows (using cloning) to get a clean texture. I can then use this with a separate brow prop or paint new ones on top in the color i need.