You like looking at your dog's balls flopping about?
or is this a masculinity issue. You feel that neutering him will emasculate him. Or worse, neutering him is like neutering yourself.
Get over it. A dog is not a human. He doesn't give a flip if he's got balls. He KNOWS he's male, its a deep rooted part of his very being. He doesn't need a pair of hairy avocados hanging from his groin to tell him he's male. Other dogs won't think he's less of a male, or make fun of him. They will smell the lack of testosterone and move on. Big whoop.
You are placing far more value on your dog's nuts than he does. He licks them when they itch, that's about as far as his thoughts go. A male dog doesn't know what they are for or what they represent to a human.
and you know what's worse? If your dog were to become a stray and end up in a shelter, they would put him through the neutering procedure all over again. Only to find a pair of silicone lumps in his scrotum. And they'll sit there, bewildered and confused that someone would stick a pair of fake nards in their neutered dog.
Neuter the dog, don't give him fake nuts.