Amazon has the 2-Pack Chuckit! Tennis Ball Dog Toy (Large) for $3.23 - $0.97 off coupon (check "Save an extra" box, eligible on first S&S order for this product) - 5% off with Subscribe & Save (can cancel at any time) = $2.10 with free shipping on $25+ or with Prime. 

Made of extra-thick durable and high-bounce rubber.