Replacing a backpack should be easy, but what you can buy at a reasonable price tends to be cookie cutter. After searching and scrolling for a while, I decided to just fix the one I had and add a unique flair.
If you are going to sew on leather, make sure you have the correct needle. If you will be sewing through several layers, consider using an industrial sewing machine. The last seam around the backpack to connect the back to the rest of the bag turned out to be quite tedious on a conventional machine.