Spotlight sells "Dance lycra" including metallic varieties, it'll do the job, but the patterns (such as horizontal stripes, zebra print polka dots) are kind of hideous and the plain fabrics are in really gaudy colours. I've made shorts before out of stretch velvet and that works well, and would make for a nice leotard too, you can't see the seems as well so it's okay if you mess up or sew a little crooked.
It's also worth a look in Lincraft, I'm not sure of the quality of their lycra (thickness, wear), though they do have a larger range of just plain colours. Also look in local craft/sewing shops.
You can look at spandexworld.com for fabrics too.
If you're looking for cheaper leotards without the hassle of sewing I recommend you look on etsy. There are a lot of gym mums and dads that make cheap leos and shorts, some even making custom orders that ship to Australia.
Have a look at Gym Critter on facebook too, they will make custom leos and shorts, based on your colour/fabric choices
Also ebay if you want second hand (even new) leotards on the cheap. I've picked up a $15 brand new (scrunchie. tags and all) GK leotard on there, and plenty of other new leos for under $30
Then there's discountleotards.com