Look for texture sets that list a brow transparency map (Renderosity sets usually have a file list in the readme, DAZ sets usually list what maps are included and their sizes on the main page and may have a full listing on the wiki page). At best those will be the ones with no brows on the skin, so you can use them simply by hiding the eyebrow part, but in some cases they will (especially if they are marked as Poser only) be a mask that is used to modify the colour of the painted-on brows without affecting the skin - in the latter case you might be able to get rid of, or at least partially obscure, the brows through the Shader Mixer.