If you have not been introduced to Decathlon products you are missing out. Decathlon is a French company that is very big in Europe (so I'm told). Just this year they launched a stateside store and now have an America-specific website. https://www.decathlon.com The Decathlon products I have purchased have all been great quality. The biggest surprise is that they are almost always 50+ percent cheaper than name-brand products. I put this to the test when I just purchased a Quecha 27L Helium backpack for $40. This pack is designed for hiking but I thought I would give it a try for my MTB rides.
The first thing I noticed is the size of the pack, it is big! The 27L size might be larger than some like to ride with but there is a 17L size for $45 (go figure). The pack is high quality and comes with a water bladder. It has belt strap pockets for sunglasses or a (smaller) phone. It has a large center pouch and a quick access outer zipper pocket. It even comes with a waterproof cover that snaps onto the bag to protect your stuff on those rain-soaked rides. It has been a very stable pack during rides.
This pack is not perfect. It does not have a ventilation back and it does not have a spot to attach a helmet. High-end backpacks like the Osprey Raptor packs or the Henty Enduro packs are still better overall. However, if you just want a good pack and don't want to pay over $100 give the Quecha backpacks a try! See more at https://www.zionbikes.store