An update that I thought might help someone else. A few of the official Apple buttons are accessible. Here is a
list of UIBarButtonItem.
There is also a
thread with a code chunk on how to use it, and discussion on the risks of getting rejected if not used appropriately within Apple HIG.
Unfortunately, I still don't see a way to get the icons used in the iPod app (e.g. Podcasts, Songs, Videos, etc.). If anyone knows different, please shout!