This hiking backpack closes with, among other things, a buckle and lid. The material of choice for this bag is polyester and it has a 45-litre volume.
From Amazon
Regatta Highton 45L' Hardwearing Hydration Detachable Raincover Zipped Lid Pocket Travel Hiking Backpack Rucksacks - Black/Ebony, Single
Robert Dyas
Regatta Highton 45L Backpack Black/Ebony
OnBuy
Regatta Unisex Highton Rucksacks