You could step into a bicycle repair shop and ask for valves from old tires. They’re also called Dunlop valve, Woods valve and English valve.I shortened my cylinder a bit and it’s still working great.
Yes, the Woods/Dunlop valve seems a very good choice for DIY pumping equipment, in localities where these valves are readily available. I mentioned this possible use of Dunlop valves a long time ago on “another” forum that I now no longer attend. My first bike as a kid was a rusty old second hand one which had Dunlop valves, however, I have not personally seen these valves in my part of the world for at least ten years or more now. About one year ago, I did enquire at a major bike store here about the possibility of obtaining some new Dunlop valves and the salesperson said as best as he knew no store here sold those valves for many years and that I would probably have to buy them myself from an overseas source!
My understanding is that Dunlop valves fell out of favour in many places around the world as the Schraeder (car tyre) valves were more convenient as you could pump your bike at any gas/petrol service station using the provided car tyre inflator without needing an adaptor. I believe the Dunlop valve may still be commonly used in India, parts of Asia (Japan?), and Holland. Even though they are also called “English” valve, I think they may no longer be commonly used in England these days.
For DIY pumping equipment: Car tyre valves are too fat for the commonly available 1/4 inch aquarium air hose. I am not familiar with their use but another common type of bike valve here are Presta valves, but they do not appear at first glance to be suited either. The Dunlop valve would have been my choice if they were still available here.
I just remembered, our old garden wheel barrow that has a Dunlop valve, and if that valve ever becomes faulty we’re in for big trouble to find a replacement for it!
Piet, you are over there (Holland), perhaps you could do some research for us all! Do you know of any bike shops that will do mail order of these valves to the world? Websites?