When I was a kid I had a a beautiful book that was a collection of Christmas short stories.  It was lost somewhere, and I can't remember the exact name or the publisher or anything.  One of the stories was about a little polar bear that wanted the job of carrying a rainbow back to Santa to decorate the Christmas tree.  The little bear dropped the rainbow and it broke into lots of little pieces, but Santa used all the little pieces to decorate the tree and that was the "origin" of Christmas ornaments. 

The title was something something Christmas Treasury or Christmas Stories.  Please help, I would love to find this book!