A quick Google search yields this[0] which would probably do the trick. Just beware of browser compatibility[1] (something that plagues several features of Papa already, hence it requires a modern browser to use them).

[0]: http://stackoverflow.com/questions/3665115/create-a-file-in-...

[1]: https://www.google.com/webhp?q=max%20length%20of%20data%20ur...