I use Soft & Bright which is the poly equivalent of W&N but half the price. It's a really nice soft batting with a scrim. I buy it by the bolt on Amazon or Walmart.com, my last bolt I got for less than 90 for a 25yard 90'wide bolt on Walmart. The price fluctuates quite a bit though, so it can be frustrating. They both carry the cotton bolts too.
I think the Fairfield company makes a cotton batting too (Soft & Toasty) that's really nice, Pellon makes some nice battings too, they have the usual all poly, all cotton, and the 80/20 blend and they carry those on Walmart.com, you can get a 9 yard 90" wide bolt for around 30 for all cotton Pellon batting