I've been after this particular poster for many moons now, and have only ever come across originals which are usually in worn condition and fetch prices of £150 upwards!
Finally I managed to find a reproduction for a far more acceptable price at the 1940's Society! The original poster was part of a set produced during the war to encourage the purchasing of Savings Stamps. 'Soldiers at Sea' and 'Guns Behind the British Barrage' were other subjects covered amongst others.
I bought the poster which was delivered quickly and well packaged and then had it affixed to 15mm MDF, laminated and black edged which I can then hang on the wall rather than having the whole thing framed and glazed.
Link: 1940 Society