A friend forwarded a link to the Purina Pro Plan Roasted Slices giveaway on Facebook. Like them and then enter your information to get your free coupon. The page indicates that the product is available exclusively at Pet Specialty stores, so may be a bit harder to find.
I'm not sure when this freebie will end. There was no number of coupons listed, nor a specific time frame. Try sooner rather than later.