Hi Nick, There is a few industrial antique typ stores on King St in Newtown, after where it splits from Enmore Rd. There's also one in Alice St, which runs of the right of King St in the same section. There's also an intersting place in marrickville called reverse garbage, which also has a 2nd hand store on site, along Addison rd, near Illawarra (? i think).
Have fun in Sydney. If you're looking for industrial things to photograph, I can highly recommend Cockatoo Island.