How about Vedalken Orrery? while not a protective card in the strictest sense, playing at instant speed means being able to wait out the perfect moment when interruption is hardest.
On the flipside, consider Conqueror's Flail's protection as well.
Edit: In the same vein (protecting a turn or the game plan, not specifically the commander) Nightcreep could work as protection as well
On the flipside, consider Conqueror's Flail's protection as well.
Edit: In the same vein (protecting a turn or the game plan, not specifically the commander) Nightcreep could work as protection as well