Simple solution: A startup firm that warrant canaries FOR you. Every week your company receives a phone call. The pre-arranged contact is asked "Were any federal subpeonas issued for you to disclose customer data in a blanket fashion?"

The normal reply would (hopefully) no. Otherwise it might be "no comment."

I believe this would absolve the contact in question from perjuring themselves under the fifth amendment and would be no different than those "our website is hackproof" badges that get sold.

If someone wants to run with the idea, I'm game.