We use this one:
http://www.princelionheart.com/site/f_7000.html
i like it because DD can get in and out on her own. Very easy to clean.
We also has this one:
http://www.amazon.com/Fisher-Price-Precious-Planet-Healthy-Booster/dp/B001GQ2RXK
i didn't like it at all. Hard to clean, has to be strapped on and isn't as easy for her to get in and out.