Boots of Speed (Warcraft III)

Increases the movement speed of the Hero when worn.

These boots are a favorite among orcish light infantry, where they provide a speed boost to leaders consigned to ground movement. The boots of speed are created using the tanned hides of kodo beasts treated to remain soft and comfortable on the inside while protecting the feet from rocks and other obstacles.

Source
These can be bought from Goblin Merchants.

Arthas can find one in March of the Scourge, chapter 5 of the Warcraft III human campaign, The Scourge of Lordaeron.

Grom Hellscream can find one in The Spirits of Ashenvale, chapter 4 of the orc campaign, The Invasion of Kalimdor.

Tyrande can find one in The Awakening of Stormrage, chapter 3 of the night elf campaign, Eternity's End.

Kael and Lady Vashj can find one in The Dungeons of Dalaran, chapter 3 of the Frozen Throne alliance campaign, Curse of the Blood Elves.