Going from a Sony Reader to a Kobo Aura ("new", not the HD), I found that the Kobo is a lot more fragile. The first one broke after a couple of months, while in a semi-hard pouch in my cargo pocket on the bus. I usually take good care of my stuff, but the Kobo turned out to be very brittle compared to the seemingly indestructible Sony.
I got a very cheap cover from ebay, and was surprised by the excellent quality. It is very durable, fits the reader snugly, and is even shaped to fit the non-flat back surface of the reader. The particular seller I bought from has quit ebay, but there are a plethora of other sellers selling what seems to be the exact same cover:
http://www.ebay.com/itm/PU-Leather-A...n/400846876448
I've used it daily for a year and a half now, it has no visible signs of wear. Recommended.