Hi
I had a similar issue about 2 years ago with my 465 and found a company S&S Springs in Victoria (
www.sssprings.com.au) - I sent them the spring from the side I had and asked them to make another 2 plus 2 more in mirror reverse cost me about $80 including freight. I got them back in a bit over a week and they came up fine
Although I just checked and I am now wondering why I did this as the 465Z springs are still available from Alpha Sports so I am assuming I can still get them in Oz, maybe they weren't at the time ??
Cheers