I originally bought an ereader cover made for Kobo, but I found the 'synthetic leather' odour to be really strong (I'm sensitive to chemicals/odours). So, I bought McCall's pattern #6091 and made my own. I have one for my Kobo original and one for my Touch. I had to adapt the pattern to fit each one, since I think the pattern is actually for some version of the Kindle. You don't have to be an expert sewer, either, since I'm not overly experienced with sewing.
I recommend these because you don't have to hold it open like a book, you can open the front cover and snap it to the back cover. It's really comfortable to hold this way.
Kobo Original cover:
Kobo Touch cover:
edit: The link for the pattern:
http://mccallpattern.mccall.com/m609...hp?page_id=104