I've used the Joanns & Hancocks fleece, and you are not going to get as great of a barrier. It is really best to use PUL or Malden Mills fleece. Those are the only ones that are really going to give you security when out and about. At home, we use the JA or Hancocks fleece pockets all the time. You do have to watch them carefully though. Ds can soak through the pocket with liners and the couch/floor in no time flat if we didn't force him to take off the diaper and go to the potty.
Unfortunately, you can pretty much only get PUL or Malden Mills online. Walk into any local fabric store, and they will have no idea what you are talking about at all! I have had really good luck ordering diapering supplies online (the same can't be said for sewing supplies...different story).
www.diapercuts.com also has pul and malden mills and tons of other stuff. I prefer the solids to the prints just in terms of holding up longer.
I, too, am a coop girl! I get my PUL from coops, but you have to wait months and months for it. You get a better price (usually save $2-3/yard), but it takes forever to get to you. If you need it sooner, order from any of the above companies with ease. Check the feedback if you are worried about it.