I know this is an old thread, but I'm also wondering the same thing. I've looked for "ula-ulas" in numerous toy stores and only found one (on Santa Fe near Pueyrredon) that sells flimsy ones too small for adults. I'm going to look in athletic stores next. Has anyone else had luck with this?
As for classes, the closest thing I've found is at places also teaching trapeze, circus, etc. I use to take Tela (silk rope) classes from an awesome chick named Mariana Gonzalez[email protected]. Maybe contact her for info re: aro hula classes...