My HD600 headband cracked but I was within warranty so Sennheiser just gave me a new pair of HD600s haha. But seeing as you have an HD580 you won't have warranty. I looked into buying the headband part for my HD600s before Sennheiser replaced them and they are just so expensive, particularly in Aus. http://service.syntec.com.au/product_info.php?cPath=1919&products_id=80679 link to official Sennheiser HD650 headband part. $190.28!! Outrageous
I'm in Adelaide btw
And they only ship to Ayers Rock.