My line-up for Japan Expo 2013!
Sollux: x (This is a wig that would obviously need some styling, as Sollux has fairly unusual hair. Here’s an example of a Sollux wig with that base: x)
Vriska: x (Assuming that your headcanon is curly. It’s the most common style for Vriska, it seems.)
Gamzee: x (The wig would need styling, but the length and thickness should do well for him.)
Eridan: x x (This is really tricky because it depends on your headcanon. You could probably produce something like this x with the wig I recommended if you have the skill. If not, an easy slick back is always an option.)