Rimblow wheel questions

I have not long since bought a '71 Dart. It decodes as having a rimblow horn wheel on it. Sure enough it does, but the previous owner has broken the centre ring on it. The part I'm talking about is the centre button part that if you were sitting in the driver seat and looking at the wheel it would be in the middle. The button has a black centre with a silver looking ring that goes around it and then the wheel. Looks like he could not figure out how to get the horn to work and ended up prying on the centre to remove it. Broke a large section of the ring off.

Anyway, anyone know where I can get another centre from?

Also, how does the rimblow horn work? I see the black part in the middle of the rim. Is that like on the Fords that have rim blow in that you squeeze the black part and the horn will honk?

I'm going to have to get in an redo the wiring on it etc. as the wire off the back is currently sticking out and not connected to anything, but I'm hopeful that I can get it to work.

Any help would be appreciated.

Cheers