I've been having another look at the russian story Adam pointed me to which is incredibly like Brother Lustig. I still haven't read through all of it, and I really do need to start writing out a plan for the adaption based on both stories, but i really like how the magic sack is introduced in the first scene in this version. As they say in hollywood: "Set up early, pay off late".

Anyway, if you want to have a read....here it is.