Here is the pattern for the faux leather rucksack I made. (add a waist belt?) You can see the scale at the bottom right. If you make sure the red line is 10 cm when you print out the pattern, all the pieces will be th.
Fully featured backpack with free sewing pattern and step by step tutorial. Has a roll over top so you can add more or less and keep the bag the right size for the contents. Great school backpack for (Diy Bag For School)
Weekend Backpack - Free PDF Sewing Pattern to Print