There isn't much different to the normal cover, just the samsung word in gold colour.
My last one was sold on ebay really cheap, when I traded my note 3 for a S5, I was allowed to keep the cover, just made an extra few USD $$$.:fingers-crossed:
It's not available anywhere, they are only sold with the phone, your only option is from service center in hong kong, USA and korea, other places may be available from where the phone was sold.
You can also try ebay or gmarket.
The white version with gold word is readly available for me in hong kong, a friend of mine who works for samsung say that you can buy this from the service center in hong kong but require you to show proof you have the phone, well I have the receipt and box still, although I don't have the phone, but the black is not available in hong kong.