J.G.
I personally use indian cotton prefolds with thirsty covers. They are bulky, but my little guy has never minded them. Now, I have a friend who uses a bamboo fitted diaper with (I could be wrong on the brand here) thirsty covers as well. The bamboo diapers seem to be a lot thinner and she swears they hold just as much.
The one's she uses are like these:
http://www.amazon.com/MamaBless-Bamboo-Cotton-Nappy-Diape...
and an insert like these as well:
http://www.amazon.com/Diaper-Inserts-Organic-Booster-Doub...
again, I am not 100% sure what brand she uses though, but these seem pretty similar.