Bags such as this one are often very roomy. This duffle bag is made exclusively from polyester and it has a volume of 32 litres.
From Debenhams
Packaway Barrel Bag Duffle Water Resistant Travel Bag (32 Litres) - Navy - One Size
The Activewear Group
Bagbase Packaway Barrel Bag BG150 French Navy/French Navy One Size Col