I don’t know if anyone has any in stock right now. I ordered my first one from Charles Quick a few weeks back and it arrived in the US in less than a week. I wanted to order another one but looks like he is out.
Naviskelp in Poland is selling the baraki valve which has been the standby choice for quite a while but it looks like he is out as well.
There was a guy on here a week or so ago in the US who is getting some made but sounds like they are not ready yet.
Those are the options I am aware of. You need to find out what kind of steering your tractor has so you make sure to get the correct valve