I ordered a wig from MatchWigs.com for a Terezi cosplay. I love it so much! It's very easy to style and very close to what I imagine a real Terezi's hair to be. The link is: http://matchwigs.com/home/67-toncore...g-cosplay.html
It does take some time shipping to the US since it comes from Singapore, but it's worth the wait for such a high quality wig. It's also very easy to wear the horns under it. My friend also bought a wig for a Gamzee cosplay and I'm saving up for one for Jade Harley. They have wigs for most of the popular cosplays from Homestuck all at a decent price. Go check them out!