I have seen plenty that are cascades grafted onto a tall straight trunk, but they were nearly as tall as me so they were out of the question.
I can understand that people don't generally buy "trees" as often as other plants, but I thought a plant that if the basis of our national colours would be more readily available!

Today I finally found one. It's not as small as I would like but you can't get everything you want, right?
I must have looked like a moron trying to pick one out. Standing there in the Bunnings nursery with 3 or 4 of them lined up in front of me, debating internally, until I just gave up and grabbed one before I drove myself mad.
Here's the winner. But I don't know very much about acacias yet so I'll take any advice you can give. Pruning especially.
I'd love to have a shorter trunk, and I think it would be really nice as a cascade. What other styles do you think would suit?