LightInTheBox offers the RKA Punching Mitts in Black or Red for $6.99. Coupon code "4448024PAD" drops them to $3.49. With free shipping, that's $12 under the lowest total price we could find for a similar brand name pad. They can be used for boxing, Mauy Thai, MMA, and other martial arts.
Note: Uncheck the "shipping insurance" box at checkout to avoid the 49-cent fee.