WordGirl keeps this set of costumes in her Super Secret Spaceship Hideout. They are identical to her usual one, but differ in color.
Snapshot 1 (9-9-2015 6-27 PM)

Wordgirl has been shown coming up with new costume designs in the episode "Two Brains Forgets", so it is unknown if she made these outfits herself or if they came with her from Lexicon. In either case, other citzens of Lexicon have been shown wearing similar outfits in the Library on Wordgirls ship, seen in "The Rise of Mis Power", so either one is possible.