Few options here:
(1) Do Arts (no math needed) at UoM. Do a math subject as your breadth. Transfer into commerce mid-year. Your arts subjects will get credited as breadth so you wouldn't of really wasted any time.
The problem here is if you're really not interested in arts, it'll be a hard slog for you. The good thing is you are at melbourne though.
(2) As per sluu001, do commerce/bussiness/whatever at another uni that doesn't need methods (i doubt there are many courses like this that don't need methods, so, this might be hard).
(3) I've seen unilearn (
http://www.unilearn.net.au/) mentioned on the UoM website. You can do it anytime online. It's fairly expensive. Methods is not an easy course, its definitely not easy to teach yourself online. Even the uni very is fairly condensed down. I know a fair few people failed the Monash one. You're getting people who haven't done math since year 10 and even then it was fairly easy-ish and chucking them into methods.
I'm not sure why you haven't done methods but in a commerce degree, you probably cant escape the math. If it isn't your thing, then, even if you really want commerce, i'm not sure if you'll have a fun time.