Star Wars again

I doodled this while watching The Empire Strikes Back a few weeks ago and found myself wondering where Luke Skywalker's conveniently Yoda-sized backpack came from. Was it something Luke took to Dagobah in his X-wing for carrying his packed lunch which got repurposed as a Yoda-carrier, or did Yoda take it to the swamp planet in the hope that a full-sized adult humanoid might turn up at some point and give him a ride?

There may be a whole backstory to this thing, hopefully to be explored in a future movie.