Chocolate lab puppy and balls

There seems to be a lot of dog lovers on here, so I thought I'd throw out my sort of problem and see what you all think.

We have a Chocolate Lab Puppy who will be 1 year on March 7. Since he was about 5 months old, we would go out once or twice a day and play ball. The ball I use for him is a regular rubber ball that our German Shepherd has chewed on. Since she has chewed on it, it does not have the hard rubber coating on the outside, although, it does still bounce. I have tried to introduce a brand new rubber ball since the one using now is a little wore out. He refuses to use any other ball.

Rex has always had a very soft mouth. When he brings the ball back to me, he is not clenching tight to it, he just drops it in my hand, unlike the German Shepherd. You have to physically pull the ball out of her mouth. Each dog has their own ball. Anyway, my husband thinks that the new balls I've tried are too hard for him since he does have a soft mouth, etc.

I even put peanut butter on the new ball. When he catches it not knowing it is the new ball, he immediately drops the ball out of his mouth.

Any suggestions would be greatly appreciated.

Thanks