If you want something eco that is easy to find on the high street then try Lush. Not all of their products are paraben free, but most are. Avoid the liquid-based ones as they put preservative in these to stop bacteria growing and use the solid products instead.
For a super natural deodorant try The Greeench. It contains herbs and oils that can help to fight oils. I've not tried this yet but those who have rave about it.