Always plan for worst-case scenarios - assume you'll be both charged with a crime and sued civily should you ever need to defend yourself or someone else using lethal force.
A website called ConcealedCarry.com has posted a comparison between a number of the different insurance programs available right now. They say they'll keep it up to date as they learn about changes in each program.
Here's the link:
I do not currently have any type of self-defense insurance coverage - though it certainly seems like a good idea - so I cannot personally recommend any of them. However, I'll be doing some of my own research over the coming weeks and will likely select one of the programs listed in the chart.