I'm in Canada so probably does not make sense to go with my supplier plus you need to buy a couple thousand for a minimum, if you were in Canada I could sell you some but does not make sense with you in the US. There are a couple US sites that sell small amounts, off the top of my head...
Bags we used for both our ducks and chickens were 250 X 560mm so 9.8 x 22 inches and they worked great, here is a photo not sure if the link will work or not.