I have looked at TX Law Shield. It provides some nice benefits for $11 a month. The benefits go beyond legal representation in case of a shooting. They also cover carrying in a prohibited place, negligent discharge, etc. If I had their policy, I would call them if I had any firearm related legal issue whatsoever.
Alternatively, if you can find a local defense attorney that represents people on gun related issues, and keep his/her contact information with you, that would be a way to go. The vast majority of us will never be involved in a gun-related legal issue, shooting or otherwise, so self-insuring is a good solution if you keep some savings on hand. I have a $1 million "umbrella" liability policy for me and my wife. It kicks in where our auto & home owner's liability limits leave off, and covers us up to $1 million. Not sure if it includes firearm related liability or not... I should look into that. If so, I think that sort of policy (at $180/year for a couple) is a much better value as it provides a broad range of coverage. What it doesn't get you is immediate access to an attorney if you have a non-liablity related incident (like getting caught with a gun at the post office).
Another, final item for consideration... If these sorts of companies and policies become more prevalent, at what point will the industry become big enough to make a policy a requirement for having a CHL... or worse, gun ownership?