A while back I asked the copyright holders whether I can convert NAB for Kindle and epub. The response was that they are currently working on an update and will only consider the request once the update is finished.
So, the only Catholic Bible alternative right now for the Kindle (and you could probably convert it easily to epub because it has no DRM), Douay-Rheims Catholic Bible
http://www.amazon.com/dp/B0033PSG1Y/