Bags such as this one are often very roomy. The material of choice for this bag is polyester and it has a 32-litre volume.
From Debenhams
Packaway Barrel Bag Duffle Water Resistant Travel Bag (32 Litres) - Light Green - One Size
The Activewear Group
Bagbase Packaway Barrel Bag BG150 Olive/Black One Size Colour: Olive/B