Sandals of Sprinting - 3xday swift action to gain +30 enhancement bonus to land speed (max double your speed) until start of your next turn. 2,300 gp.
I think there are inexpensive boots (like Boots of Agility or something, around 900 gp or so) that have 3 charges a day (renewed each day at dawn) that can increase your speed as a swift action for one round by +10 feet for 1 charge, and faster for more charges.