I've not seen one that does this, but you can do it in the UI if you're willing to spend a little time slogging through.
First, the page content data size is not easy to extract - the page content is mostly plain text, which is held in the database. Databases generally compress it at varying levels and there's no easy or clean way to say "this page takes up this many sectors on a disk". But because of this, you can generally assume that the content size is really not that important.
It's the attachments you're going to be interested in, as these are just dropped on a disk unchanged.
For each space, go to space settings -> manage pages -> attachments, where you'll find a full list, orderable by size...