We have found 4 bags that match these dimensions.
52x33x21cm 20.3x12.9x8.2"
linear: 106cm/41.4" ~36L
The bags below are not exactly the size you were looking for, but perhaps you'll come to like them.
20x12x6.75"
linear: 38.75" 28L
46x29x20cm 18x11.5x7"
linear: 95cm/36.5" 24L
47x32x20cm 18.5x12.5x8"
linear: 99cm/39" 18.8L