looking for the perfect bag (please please help a girl out !!)

Hi everyone,

I'm looking for the perfect backpack and I cannot for the life of me find one matching my criteria, even tho I don't feel that picky. What I need:

- enough room for a small city trip, so like 2-3 nights (I travel lightly) I was thinking 25-30l but if you think 20l is enough, i trust you. I plan on using it for hikes as well

- a top lid (not sure what it's called, i'll attach a picture)

- small enough to pass as small luggage in the airplane (40x30x20cm), this can be while thightening every strap it has

Please please please help a girl out, I'm going on erasmus soon and I would very much need it !

https://preview.redd.it/g6xkwmdys6ag1.png?width=633&format=png&auto=webp&s=954681e63b8a06ac0a0572e2a13414c80351f113