I just received my cheap cover from
http://www.ebay.co.uk/itm/261356533354 and it appears to be identical to @user38's cover that he posted pictures of earlier in the thread.
I think someone else already pointed out that the blue on the clasp is just the blue protective plastic that needs to be removed. The magnet protrudes about 1mm from the other part of the case and has quite sharp edges. Nevertheless, Kobo's sleepcover functionality works fine.
I'd echo everything Stephen says about it, with one addition - the cover feels quite slippery in the hand at the moment. That may change as it ages, but I feel I need to grip it quite tightly to avoid dropping it!