Instead of a bicycle grip, you can get rubber tips for a chair or stool leg at home improvement or hardware stores. Just match the diameter and cut the existing Garrett handle so the two butt up against each other. Works great!
That said, I also learned that the Lesche is absolutely the way to go. The steel the Garrett digger is made from is too soft and I had to bend mine back into shape several times.
If you call Garrett, they will probably send you a new one but it will fail, too.
If you look on Amazon, the Lesche is only about $37. Well worth it.