Sportlite 20L Unisex Hiking Backpack

I have been happy so far with the Osprey Sportlite 25, women’s size s/m. I am a little less than 5’6”. It doesn’t tick all of your boxes though since it has a zipper closure and is about 22” tall per my measurements (the other dimensions are totally smaller than your requirements). I like that it ha

My go-to bag for the Azores was the Osprey Sportlite 25L (a bit bigger than what you're looking for, but we've always had great experiences with their bags. That said, key is to bring along a bag cover, whichever pack you choose.

I’ve heard that the Osprey Sportlites are very similar to the Osprey Talons, and those have a very good reputation.