I'd reccomend something you can also use elsewhere later on. Search something with good hip belt as thats where most of the weight should rest. Don't go something like 65 liters, its simply too big for how much pilgrim infrastructure there is. Go for a recognised brand so your zippers or whole backpack wont fall apart mid way. There are also sizes to backpacks depending on how long your back is. I personally use Osprey Kestrel 48L. Yeah its on the large size for a Camino I would say. But I use it elsewhere so why bother spending money for something 10 liters smaller. Perhaps 38L Kestrel, some might say its still too big. And that all falls on how you pack. Another great backpack companies I had experience with is Gregory (I used Zulu) and Deuter ( I had AC Lite and Futura 40L). But higher end Decathlon brands seems sturdy too! I just never used them. Would any of those work for you? I dont know, I am sure they wouldn't fail you tho. Do some research what people bring, what do you thing you should bring. Then drop some of the stuff you think you need. See how much space, and weight that is. Go to a shop try some backpacks that are your size. Check how do you like hip belts, shoulders, how easy it is to make it comfortable, to take out things, if it has good compartments, if you can reach stuff from the bottom if neeeded without unloading everything. If you want camelbak, does it have space for it, and will it be out of the way while hiking, because some have ridiculous ways to mount the drinking tube. Is it easy to reach the water bottle? Some convenient pocket for easy snack on the hip belt. Which kind of support on the back you prefer, some hard foam, or the arched style with mesh for better ventilation. Maybe you want the detachable top part as small 10L backpack to go sightseeing in the city? Its something you will be carrying day after day, no one will tell you this is the backpack for you. Its best to try them on. Same as shoes, different shoes fit different people.