lol, I thought you said you did not have it. Not sure if you would have RGB masks for eyebrows, but as far as I can see you do not need them for making eyebrows for stylized character as pictured.
They are only useful if you need to shade parts of the object differently (in terms of color, texture, opacity, blur... etc).
For instance making whatever is under the red mask darker than area covered with a blue mask.
Tracer's brows are pretty much black and linear. You just need to shape curves using various transformation tools and align them symmetrically.
For reference points use a dark occlusion spot (the one that is going around the nose).
You could duplicate diffuse map and work "levels" to make a contrast symmetry reference point.
I would advise to make right eyebrow first and play with it until you find a perfect location for it.
The major obstacle is the UV stretch, which effectively deforms the shape of eyebrow at certain locations, when customized diffuse map applied to the character. Again need to play with it.
Finally just duplicate right eyebrow, flip horizontal and move it (holding Shift) to the left aligning symmetrically.
It is really hard to see eyebrows shape under the goggles but I think at the end they might require a light touch of "smudge" for edges.
Just need to practice.