Iff'n I was you, I would use
Marty Hayes' Armed Citizens' Legal Defense Network as a
baseline if you're considering such insurance.
I've listened to the sales pitches on way too many of these things - one that's pushed by a major organization (not the NRA) only pays if you're found innocent, which means "your" insurance has a vested interest in you being found guilty - I don't think I like the sound of that!
Mr. Hayes' outfit sounds like they front you money and lawyers in order to try to head off the problem, instead of leaving you to your own devices, possibly hoping you're found guilty so they don't have to pay out.
There are a couple of others that seem to follow his model, but I can't tell you off the top of my head who they are - I've listened to a number of representatives from various outfits on gun podcasts.
I think another I might investigate is
Texas Law Shield - they are in the process of going national, so you'd have to check to see if they are in your state. Their national outfit is
U.S. Law Shield.
Just cruising by their site I see one of their bullet points is
Not A Useless Reimbursement Scheme.
Shop wisely...