I have created a small component that allows game developers to create custom popups and input popups, using completely individual art. It will look better than UIAlertView in most games:
I have written a short tutorial here: https://www.makegameswith.us/gamernews/282/mgwu-popup-customizable-alertview-for-cocos2d
And the Source Code is available on GitHub, along with some other widgets: https://github.com/Ben-G/MGWU-Widgets
Would be great to get some feedback, in case anyone of you decides to use it.