Here's what I used:
100% cotton batting (Don't use polyester because it is not as absorbent.)
1 yard of flannel
1 yard of Rip-Stop water-resistant fabric
1 old towel
I bought the supplies at Hancock's. I spent about $35, and the batting was the most expensive item. I got one package of crib-size batting and it was about $15.
Layer together the flannel, batting and towel. Sew a zig-zag stitch down the middle.
Sew a zig-zag stitch around the outer edge of the towel and batting.
Pin the Rip-Stop to the side with the flannel.
Sew on the snaps.
This is the backside.
It snaps closed into a handy little pouch.