Where can I buy small internal speakers?

[woox]

I currently bought USB powered speakers for a portable, the speaker that it actually came with is too big and I want to swap it out with something smaller, the current speaker has two terminals (like this:http://www.topmic.com/5090306.html ) (I dont know the height of these speakers so i cant really buy em)

Does anyone have a suggestion of where I can get a decent small size internal speaker? I am having trouble finding the right kind, I am looking for the height to be fairly small to fit inside a portable, thanks.