Give them a time and place for their ass to appear or be on notice that a press conference will be held exposing every phone call, email, or other communications they have made refusing to do so.
Expose the cowards.
While they are at it, let everyone know that Chuck Schumer and senate democrats have been protecting Mayorkas from an impeachment trial in the Senate. Go to all red and purple states where Senate democrats are running for re-election and hold major campaigns to let them know that their democrat Senator is helping to hide the facts.