Gary,
Hello from a fellow Aussie. I'm not sure whether you have found some trim rings yet as this is an old post... try Mitch (or Ben) from Antique Tyres in Victoria... http://www.antiquetyres.com.au/ ... as they stock the 17" trim rings. They are most likely just over $50 each as that's what I have paid for both of my 16" sets. I have been dealing with them for quite sometime now and they have always been great to deal with.
Hi Dave also. Was good to catch up with at the BBQ in Lodi in April.