I bought a 350 four years ago and it came with two cases, one is the sony official, made of plastic and fake thin leathery material that started to wore out after few days of usage, the other one is this seem to be a full grain leather cover, that's really thick and durable with excellent craftsmanship and material.
photoes
http://imgur.com/a/DAseT
I recently bought another 350 in mint condition, and I want to buy the same leather case for it. But this case has no labelling or brand or anything. I am sure someone in the Sony reader community would know the maker of this case since it is such a quality case.