I'm considering this inflatable Stay Puft Marshmallow Man costume for Halloween. Every few years my Ghostbuster costume comes out of storage, but I feel like stepping on a church.
A friend has this costume and it uses a clever battery operated fan to pump air into the suit, keeping it inflated. At $30 it is a bargain.
Ghostbusters Inflatable Stay Puft Marshmallow Man Costume via Amazon