NitroX
Re... why anyone would want a 458 in a double astounds me

I handled one a couple of years back that I think might have been able to change your mind.
It sure was a nice thing and I wanted it badly but the owner was not ready to sell at the time.
Yes it was in 458 win mag and made in Europe.
It was a 9 pin sidelock ejector with 24 inch chopper lump barrels, with quarter rib and one standing-two folding rear, and silver bead front and folding nightsight.
The action had colour case hardened finish and was fully deep relief engraved showing Elephant Buffalo Lion and Leopard.
All the internal lock parts and pin ends were gold washed.
The gun featured gold inlays, cocking indicators, extended top strap, cartridge trap and grip trap (both engraved) and the stock included a cheekpiece.
The action locked up with double under bites and Greener type crossbolt.
The lumps featured huge radii at the intersection of lumps to barrel flats and similar at intersection of action flats and standing breech.
This thing was built strong!
Of course it had bushed strikers and came with the factory case.
The owner was a man who had owned a lot of quality doubles and knew what he was talking about.
He pointed out to me that about the only thing missing was a rolled trigger guard.
It was a lovely gun, had been used a little, and was still nice and tight.
Sure it had those piddley little extractors that you often see on doubles chambered for rimless cartridges and I wouldn't trust them on dangerous game, but who cares.
It would have been a great rabbit gun!