go to the wreckers and get some plain wheels for the time being. you might find it hard getting them with tyres because they probably go to the second hand tyre places, but you may
that said, try the second hand tyre places. 205/65/15 are a very popular size for larger cars and shouldn't be hard to find. i found some the other day cos i just got newies on the front, but they didn't quite have the amount of tread i wanted - they were $55 each, for yokohamas.
for me they would only have lasted a couple of months i'd say, so i turned 'em back. that was in townsville, you should have heaps more luck in brisbane.