Supergirl's costume is changed all the friggin' time. It's as transient as Lady Gaga. DC just can't seem to find a look they're satisfied with. Unfortunately, they've already passed by the greatest costume they've ever devised. They used it in Adventure Comics #415, laughed at it within the story itself, and then it was never seen again.
And I only know it exists because of a comic scan from Girl-Wonder.org.
Despite the in-universe derision of it, I am in love with it. There's just something that's playful and energetic and utilitarian about it. C'mon, it has pockets! Wearing it, you can see she's excited to be a superhero. Plus it doesn't make her look like a teenage sextoy.
So I had to draw it.