[zumarrad]

*cries* But it's so pretty the way it is!

I would say you could just chop the top off. Where does it zip/fasten? Split down that seam and replace with hooks, with perhaps some kind of flap underneath to handle the overlap, if there isn't any already in it.

It will probably need some kind of unstretchy tape around the bottom hemline to help it hold its shape, if you want to leave it very stretchy, or - if it doesn't really need its stretch - you could sew it onto a firm base.