Gun owners already have insurance to replace stolen guns. (aka household insurance). What you are talking about is a "Sin tax" on the law abiding to pay for the actions of criminals.
Personally, I'd encourage gun owners to store their guns in bolted down safes but if they don't and a gun gets burgled from their house then I think that 100% of the moral culpability and the legal punishment should be on the burglar. (at most one could say that the gun owner had taken a risk... Nothing more).
Talking about risk versus culpability; Tell me, if someone decided to walk home late at night, through a bad neighborhood with poor street lighting and they were robbed or raped... Wouldn't you say that, while they had perhaps taken a risk, the entire moral and legal culpability should be laid on the robber/rapist? And that we shouldn't punish the pedestrian for doing something wholly legal (even though, due to the presence of bad guys in the world, it was risky). You wouldn't, say, Levy a fine on them... Would you?