Early in World War II, James Wright was working in General Electric’s New Haven, Connecticut labs, under a government contract to create an inexpensive substitute for synthetic rubber. One day in 1943, Wright happened to drop boric acid into silicone oil, and was astonished to find that the resultant goo would stretch and bounce further than rubber, even at extreme temperatures.
You can make your own or order mass quantities from the manufacturer.
You can even drop 50 pounds of Silly Putty off of a parking garage.