I've seen ROML Mystique body used for Mockingbird once or twice and I have to say it works perfectly. I went with the 2-pack Invisible Woman head since I had it in my fodder bin, saving it for a rainy day. The glasses are cut out of a plastic clam shell figure package and painted with clear yellow Tamiya paint. I sculpted on some other outfit elements like the arm bands and part of the boots. The studs and buttons on her costume are little sticky "beads" from the dollar store.

Body: Mystique
Head: Invisible Woman (2pack)
Lower Legs: Hope Summer
Hands: Elektra (2pack)