Same. Never seen a DA20 single pilot type. Would be pretty fun though.
If I remember right, the Lear 23 was originally slated to be certificated for single pilot ops, but the FAA eventually deemed it too complex for one pilot.
Of course, Bob Hoover flew his aerobatic routine single-pilot in his Saberliner 40, but that was a special FAA exemption for the pilot, not necessarily the airplane itself being certificated.