I'm happy enough with the sound of my piano, but the action stinks. (Overdamper, loop and wire.)
I'm prepared to put another action into a new frame, but that amount of tedious work might as well have a brand new action rather than something from a scrap piano.
So what will a new upright action cost me, and what's the best one to ask for?

You have what we call in America a "birdcage" action. I've seen 4 of these in 20 years in the Chicago area, and I'll be happy if I never see another one. It is a bad design, and difficult to tune. All have had loose tuning pins as well.

My advice to you is to dump the piano. Trying to custom make a standard type action for that is more than a new piano would cost, not to mention the additional cost of replacing strings and pins, which I'm sure is needed as well.

Each piano model has an action specific to that scale, so I doubt if you could find a junk action that would fit properly.

If the cabinet is nice, you would be better off putting in an electric keyboard, and making a digital piano out of it. Just a thought.

the birdcage action in itself was actually a decent design. Many of them eleviated the problem of lost motion when the hammer line is raised. But...

There's no use trying to fit a new action into an old piano. The piano wasn't designed to hold any action but the one that's in it. The strike point would change, the geometry would of course change, and everything around that would change. The piano would no longer perform properly, or feel good to play. The absolute BEST case scenario would be that you would spend a lot of money, and time, and end up with a crappy old piano that had a shiny new (but not working right) action in it.
Nice cabinets also make great wet-bars ... just a thought.

Save up a bit and get yourself a new instrument, I think you'll be happier in the longrun.

KlavierBauer