I got the pattern free from Sew Liberated. It's the Montessori Childs's Apron on the right hand side.
I finished off this lined leaf pouch/bag on the weekend and sewed the boys some bags for adventuring. Mostly to avoid the pockets full of stones and bugs and leaves that we sometimes end up with. #1's one has a rainbow strap (used his old toddler harness!) and #2's has a cute monkey patch. Tested them out on our Sunday walk and it was sweet.