While I agree wool and fleece are preferred by many, PUL is thinner and also the #1 choice for some, including myself. I find wool too high maintenance and I could never get the hang of lanolizing. Fleece I find too bulky and you need two layers to make it as resistant as PUL.
You can get PUL from wazoodle.com , it ships fast in Canada but slow to the US.
BUt the biggest makers of PUL right now is Fabrite and they're going through some big changes right now so it may be hard to get some.
You may also want to check out the fsot section of www.diaperswappers.com
to get some PUL