Are the older 72 AC POA valves extinct?

[Lugnutt]

I've been looking and looking to see if I can find a replacement for my original POA valve for my AC. It seems like nobody makes replacements. Please, does anybody know of anyone that makes new or rebuilds these? Or can these POA valves be repaired and re-used? If possible, I would like to keep my old system functioning like it did in 72.

I don't know why I'm reluctant to upgrade to a cycling system, but I am and I sure could use you guy's help if it's possible.

Thanks, and I'm sorry if I'm being such a stic-in-da-mud on this.

pic attached