Cheapest priced copy (Outlaws of Thunder Junction Commander): $2.99 at Card Kingdom, near mint, their price list as of .
Swiftfoot Boots 
Artifact — Equipment · Uncommon · Commander 2018 · #225
Equipped creature has hexproof and haste. (It can't be the target of spells or abilities your opponents control. It can attack and {T} no matter when it came under your control.)
Equip {1} ({1}: Attach to target creature you control. Equip only as a sorcery.)
Legal inCommanderBrawlStandardPioneerModernLegacyVintage
Not legal inPauper
46 printings · $2.99 to $37.99 at Card Kingdom
One ruling from Wizards of the Coast
- 16 March 2018If a creature enters the battlefield under your control and gains haste, but then loses it before attacking, it won't be able to attack that turn. This means that you can't use one Swiftfoot Boots to allow two new creatures to attack in the same turn.