Ha ha ha ha ha! very funny!!! Sorry only kidding, just speaking from experiance. I have a used 2mm oversize wiseco if it is any use? The rings are still a stock item from wiseco. failing that you can bore it out to accept the standard 480.
as for the rod kit good luck.
do you have a series one or series 2 450?
also have you checked the crankcase where the clutch shaft bearing sits? this is a favorit for ging way ( as i found out)
America is your best bet for a rod
hope this helps
Kris