It ought to be possible to find a replacement (not sure about the size but I do know it's not a hollow key that it needs). The inside has been left untreated (would be good to treat with an oil which moths don't like and which make your linens smell good) and there is a "candle shelf/box" on the left-hand side with a secret drawer underneath (which is awkward to pull out, given that there is no handle- I'd fasten something discreet to it if using the secret drawer, but I never did) both made from the same hardwood as the inner lip. The blue chalk paint is incredibly hard to photograph but it's best seen in the detail of the runners on the bottom (reminiscent of those runners you get on steamer trunks, complete with rounded ends so that they can be pushed and pulled on and off steamers, coaches and the like).
If you are interested it is Everlong's Amble Sea (which I thought was rather appropriate for this piece) which is top left in the colour chart (see photos). Width: 93.5cm at the widest. Depth: 48.5cm at the deepest. Height: 48.5cm at the highest (including the runners which are roughly 1cm deep). C ollection only: As with all my furniture, it is collection only.
But that means that I will happily work with your courier (Shiply is great for finding someone to transport it for you) should it not be possible for you to collect in person.