Duffel bags are easy to squeeze into tight spaces. This bag is made from polyester and it has a 32-litre volume.
From Debenhams
Packaway Barrel Bag Duffle Water Resistant Travel Bag (32 Litres) - Jet Black - One Size
The Activewear Group
Bagbase Packaway Barrel Bag BG150 Black/White One Size Colour: Black/W