How to fix a thinning hair?

hi friends, 

As you can see in the attached image, I have some thinning hair issues 🙂 

Any way I can fix that? the footage is pretty static, I'm sitting on a chair, playing my guitar. so my head is basically just moving up and down a bit. 

I was trying to put a mask and track its motion, which is quite ok I guess, but the "gaussian blur" is really not the solution to apply here. it looks completely corrupted. is there any other color "filling teqnique" I can use? 

Thanks!