I know I had investigation insurance with my accountant a while back - you paid them an extra £50 or something on your tax return and then if you got investigated by HMRC, they’d cover the cost of their time in negotiating with HMRC, sorting out the paperwork etc.
I’ve never heard of it for bookkeepers though - you aren’t responsible for the content of what HMRC gets given… So how would you be able to make sure they or their accountant hasn’t screwed up?
That’s like asking a salesperson to be paid on results only when you supply the list - it could be incredibly duff leads.