If you want to do it legally, you get a reptile keepers license from the link below, or a pet shop that sells reptiles. Then go to a pet shop that sells reptiles (Pet Magic in Cannington does) and buy some. If you don't want to do it legally, go find some natural bushland up at Armadale, Roleystone or down in Mandurah and wander around at night with a torch and bucket.