If we are talking unaltered typical '98 Mauser actions, I don't know of any non-wildcat .40-.43 caliber cartridges that will fit in a standard length Mauser action for which you can get commercial ammo. The .404 and .416 Rem are too long and ammo isn't easily available for the others that might work like the 10,75x68 or .425 Westley Richards.

The .404 and 10,75 nominally take the same .424" diameter bullets. With older rifles what the actual barrel dimensions might be of either is open to chance.