A friend of mine has a massive GSP and he LOVES this ball, when I was there I could tell how durable it was.
My pup Dobby has had his since Christmas and it definitely has battle wounds but he hasn't been able to murder it. It's his favorite toy to play fetch with as well.
KONG - Jumbler Ball - Interactive Fetch Dog Toy with Tennis Ball (Assorted Colors) https://www.amazon.com/dp/B00KNWVPFO/ref=cm_sw_r_apan_i_YQY088095YG88T3GW14G
You can find it at pretty much any pet store near me and it seems very durable! Maeby has spent hours gnawing on it to squeak it and trying to get the tennis ball inside http://www.amazon.com/KONG-Jumbler-Large-X-Large-colors/dp/B00KNWVPFO