Sure you can buy one just like it in the store but PVC pipe is fun to build with.
Step 1: The Bag
The bags are sturdy cotton and are roughly 32 inches long and 27 inches wide. They have a drawstring in the top and a little spring loaded barrel tie. They're nothing fancy.
If you were to make these, you would need 2 panels 35 inches long and 28 inches wide. You would sew both panels together around 3 sides approximately 1/2 inch in from the edge leaving ond of the 28 inch sides open. You would then fold the edges of the open side down 2 1/2 inches and sew around the circumfrence of the opening 1/2 inch in from the edge of the fabric (2 inches in from the fold if you are so inclined. After that you turn the whole thing inside out and cut a little hole to thread your drawstring through and get to threading.