At a capacity of 20 litres, it would be better to get a backpack and just stick it on a trolley. The backpacks are decent these days - with a way of controlling the flow.
Alex has come up with some decent innovations over the years but, although I haven't seen one in the plastic, I suspect that this doesn't reach the usual high standards.
I could be wrong of course. I suppose it could suit someone working from a car who hasn't room for a separate trolley to put it on.