You can find a whipped soap base at
www.wholesalesuppliesplus.com it's the Crafter's Choice brand, it's very nice. One thing though if you're making bath bomb cupcakes, honestly I recommend using the following recipe rather than a whipped soap. Unless you add some melt & pour to the whipped soap base, it won't harden. If you're going to try to make your own whipped soap, it does get rather hard to pipe the frosting since it hardens so quickly. I use this recipe all the time & they come out perfect 99%
Hope this helps you!
http://soap-queen.blogspot.com/2009/03/ ... sting.html