Disclaimer use this toy method at your own risk.
How to get your cat to play alone with a balloon. You can tie a feather to the end of the balloon string or something else that will float with the balloon for added fun.

Angel has found that playing with the string of a helium balloon is very fun. It allows him to grab it pull it down while it wants to consistently pull up like natural prey resisting. hi come home and find balloons all over the place and I know he has had some fun while I’m away at work.