"Banded" rims are not legal in Australia...
Normally you supply your centre (ie an old wheel) and the wheel place will source the rim and weld it together to the offset you specify (within reason). Cannot help you in NSW, but I have had a number of ones done for my Renault Motorkhana Special by a place in Lilydale (Melb). Renaults come in a massive 3.5" wide and I needed at least 7" for the slicks, so I went for 7"...... Was going to go 8", but they could not source any blank 13x 8" rims(They were prepared to cut and shut two 7" rims for me as it did not have to be road legal, but it would have cost more than twice as much as the 7" version)
Costs are about $120/wheel.... (there used to be 2 places who did it in Melbourne)