Just buy a this one from Amazon UK, from Tomy Toys and they have it shipped directly to you from the manufacturer in China, I love mine, plus the price was great, I could buy 3 of them for the price of the DJI model. There is another thread posted with pics of mine loaded up here, do a search for "Hardcase backpack advise"
My favorite case is the Go Professional case. It comes in a compact version(good for carrying on to a plane) and a wheeled version. You can find a bunch of other commonly used P4 cases here.