I was scrolling through the SFM workshop, and I found this:

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1617628605&searchtext=punks

I downloaded it, and found the model for the hair only. Then, I managed to precariously fit the hair (as much as possible, because his jaw bones are to defined to perfectly fit the sideburns) onto the spy's head, making possibly the most perfect Robbie Rotten hair possible in SFM!