I'm pretty sure that the original covers were not made of leather, if you have lost yours perhaps you might be able to find a replacement on ebay.
This thread might help you:
https://www.mobileread.com/forums/showthread.php?t=52969
I'm guessing that you want a book like cover, not something like this?
http://amazonbookworm.com/2010/10/19...-ebook-reader/