Nappy Wallet Bees Kneez
Ro'Shell
They are big enough to hold 4 cloth nappies or a tonne of disposables, wipes, creams etc.
They have a strap that can be used to hang the wallet from a pram or trolley, the strap can also convert so the wallet turns into a shoulder bag.
They are great if you don't want to carry a heavy nappy bag everywhere or to keep your nappy bag organised.