My wonderful friend and leatherworker, Margaux, only about a week after me requesting it, made me an amazing pouch, which is the third item on the costume list. It seems relatively simplistic in the comic, with a drawstring tie, sometimes it is depicted as being wrapped around his wrist:
It's awesomely true to the original idea, draw string like the more complex one in the comic, and also has a little Margaux flare with the red lining so that it can actually hold sand.
Check it out!