A business suit or fancy dress clothes
Find a nice business suit or fancy outfit that makes you look like a rich Wall Street banker. A tuxedo and top hat would work as well, if you want to go for more of a "Monopoly man" type look.
Think rich, preppy, and executive-style when fixing your hair and adding accessories. As with many other funny costume ideas, this works best if you play it up to the extreme with a fake fancy watch for men and over-the-top jewelry for women.
To emphasize that you are a bailout, carry a bucket full of play money. A metal bucket looks best, but plastic will work as well. If you'd like, you can label the bucket "Government Bailout". To be really frightening, go around asking for contributions to the bailout fund.