Wow..yep...that's a tough one to find! Costumer's Guide has a great picture of the screen used bustier but only from the front.
The action figure shows it as lacing up in the back.
Given that the Silk Spectre II action figure is pretty bang on accurate, I'd have to go with that being a pretty good rendition of what it looks like. Unfortunately, that's all I was able to find. Hope that helps a little.