Oh sorry I was thinking the internal tubes that go inside the springs, yes I see your problem, a few here in NZ looking for fork tubes too, must be something that if not looked after over the years degrades quite quickly.
Best of luck in your hunt, you have more chance of scoring some in USA, I had to get my 79 exhaust set from Texas so I know the problem.
Try contacting Soos on here, he usually has some of the strange bits for 650's.