We use a standard, large IKEA bag, which then contains the original bag so that there is also room for the accessories. Has lasted for more than 30 uses.

We use a North Face Base Camp Duffel bag, 150 litres. Very robust and waterproof except for the zip, so we can tie it to the back of the boat on the water with the pump etc. inside. The bag is big enough with the boat for all the necessary accessories including life jackets, practical for travelling by public transport.