These double pocket wetbags from Bubblebubs are an absolute must for life with kids, whether you cloth nappy or not.
Hold your clean nappies in one pocket, and have the dirty nappies in the other.
These can also be used to store wet, dirty clothes (accidents, muddy puddles, sickness etc.)
They can also be used as a swim bag, put dry items in one pocket, then wet in another.
We always keep one in our car and one in our nappy bag for just in case.