Have you tried making your own silly putty? I learned this recipe 15 years ago when I worked at a preschool. I still think this is the coolest stuff!
Mix together 1 part liquid starch with 2 parts Elmer's Glue. At first you'll think you did something wrong because the two ingredients don't seem to want to come together. Don't give up, keep mixing! Use your hands if you have to. Pretty soon you'll get a wonderful, gooey, white and shiny substance. Your kids will love it! Set them up at the kitchen table. You don't want this putty to get on any carpets because it sticks. If your kids get this on their clothes, no problem, it washes out.
Give your kids a pair of kid-scissors and let them cut the putty into small pieces. Your kids will spend hours cutting their putty snakes into little pieces, smushing them all together, and starting all over again.
You can find liquid starch in most grocery stores in the detergent aisle or at Walmart. Any brand will do.
Store your silly putty in a ziploc baggie in the fridge. It will last indefinitely.