Our backyard has pieces of toys scattered all over it..lol. I got a hard plastic ball from The Reject Shop (a real cheapie..it was only a few dollars). It has a hole in it and i put his biscuits in there in the morning. He absolutely loves it and so far hasn't managed to destroy it, he's had it for quite a few months now. Very funny- after dinner every night without fail he will go and find it and throw/roll it off the verandah then go and fetch it again..makes a lot of noise but boy it must be fun!

We also bought from the vets last time we were there a big ball (maybe around the size of two softballs put together? But they also had smaller ones for smaller dogs). It's kind of like a tennis ball, has the same sort of material on the outside and is hard but squishy...sorry that probably doesn't make much sense but I dont know how else to describe it. Lol. He hasnt managed to damage that one at all yet either. It was only about $12 from the vets..so kinda expensive but he hasnt destroyed it yet.