Surprisingly, for many people, buying a new flageolet is not an impossible proposition. Although flageolet-making has hugely declined in the last century, there are a number of people who still make traditional instruments. One of my aims for this site is to seek out people who are willing to continue flageolet making and encourage them to take up the challenge so hopefully this list will continue to increase in the future.
At the moment, the main source for new French flageolets is the English recorder-maker, Charles Wells. His instruments are based on the traditional recorder-style design (as played by Thomas Greeting, Samuel Pepys etc.) and are very reasonably priced. As well as producing instruments in the standard key of A, he states that he is willing to make other keys to order.
Alba Whistles is a Scottish company which specialises in making high-quality penny whistles. They also make the late-style English flageolets, keyless instruments constructed entirely out of metal. As one of the best manufacturers of tin whistles in the country, the quality of these instruments is assured, although it is a shame that they are keyless.