Can anyone help with this project?  I need to make a cake topper of an elephant holding a balloon in his trunk.  The balloon needs to float.  I was going to use floral wire to attach the balloon, but it will not hold the weight of the balloon.  (Balloon size is about 1.5" in diameter so it's small).  What should I make the balloon out of?  RKT would be too heavy as would gumpaste or fondant.

Have you tried to use a thin bamboo skewer?  That may work better.  You can always cover it with a thin layer of fondant.

A foam ball. I use varying sizes for all kinds of things. Cover in fondant/gp whatever. I like using fondant, so you can work it smooth longer.

you might be able to make a balloon out of gelatin.  theres a video on youtube that shows you how to make gelatin balls.  im sure you can make them into the shape of a balloon.

AI agree with the gelatin balloon. It would be lighter and the foam ball wouldn't be a bad idea either. Makin a solid balloon out of fondant or gum paste would be much too heavy.