This model of bag can hold 41 litres. A soft casing is easier to fit in tight spaces and there are multiple handy storage compartments.
From Amazon
Samsonite Airea - Spinner S, Carry-on Luggage, 55 cm, 41 L, Blue (Dark Blue)
The product is available from £123.03 at international stores.
Case Luggage
55cm Strict Spinner - Airea