I have a left-handed 458 Lott, but like others have mentioned, it's a custom job. It's an older Rem700 458WM that had a chamber reamed to Lott. It's an okay route to go if he wants the Lott rather than that winmag.

Fair warning though, the Lott is a devil to shoot, even with a merc recoil cylinder and a comfy soft decelerator pad.

The hunter does not hunt in order to kill; on the contrary, he kills in order to have hunted. --- Jose Ortega y Gasset, in "Meditations on Hunting", 1942.