Just get a metal valve cap or a metal valve extension and attach a hose to it. You do not need to buy a tractor valve or a $90 valve to do the job.
Actually the very first one that I ever pumped up I used the hose from a foot pump with the little lever to lock it in place. It kept blowing off but it did eventually pump it up.
This is the end on my pump. It is made from a valve extension that has been silver soldered to a brass fitting.
And this is my hydro pump. It is made from a Mini plastic tank master cylinder and is fitted to a Morris 1100 pedal box. The ice cream tub gives it a larger capacity so it does not need filling every 4 strokes.
I did the same, I soldered a brass valve cap into a 1/8BSP brass fitting, then used 2 Mini front brake hoses and a bit of pipe. The MC is a tin tank one on a Fiat 124S pedal box. I top it up every 10 strokes.
