If you want durability, you may look for second hand stuff from big brands online. I know a couple of youtube channels that sell such stuff and even do giveaways. Now choosing a backpack was a more serious issue for me personally. I went through five of six online stores before I found what I needed. Maybe I am just choose of course. I try to do it according to practicality so buying cheap ones is not an option for me: http://tenres.com/. I have the one I like now even though according to experts there is still room for improvement.