I can highly recommend the Mulbess cases; I have the Wine color. I also have the one that dordale mentions above, in the teal color. But I do prefer the Mulbess case as it's much sturdier and feels more "solid" when I hold it.
http://www.amazon.com/Mulbess-Premium-Genuine-Magnetic-Function/dp/B00GXV4UNS/ref=sr_1_2?ie=UTF8&qid=1409488056&sr=8-2&keywords=kobo+aura+hd+case+mulbess