Sorry, the devil made me do that! The idea of speakers concealed inside a costume is very creative. I'm not familiar with portable speakers, but there's a tradeoff between size and bass extension, and usually between price and sound quality, that will make it very hard for you to find a pair of speakers that can easily be concealed inside a costume and still sound good. The lack of "high end" quality probably won't be an issue in a noisy party environment, but the lack of bass extension and inablility to play loudly will be a noticeable distraction.