We are loving these double wet bags, here at The Nappy Gurus. The small is perfect for wipes - wet & dry (given the double pocket, yay!) The medium takes a couple of nappies and the large can store around 6 nappies (size dependant) . They also come with a popper handle so you can hang them in your changing area, over your buggy or off the door handle.
This removes the need for two wet bags, if you tend to find it a bit of a faff when out. Easy peasy, problem solved!