I bought the commonly available inexpensive third-party Kobo Aura and Aura HD sleepcovers off eBay. You know, the ones like this:
http://www.ebay.com/itm/New-Auto-Sle...item35cf557407
They're actually very nice, but they both have the same two problems compared to the official Kobo Sleepcovers, which I also own.
First, there's no real indentation or lip to get your fingernails/fingertips under to pry the cover open; it's a bit awkward.
Second, the magnets used on these third-party covers are much stronger than the ones Kobo uses. Yes, they'll do a better job of keeping the case closed in a bag or purse, but they also make it hard to pry the dang case open.
The solution? I had an old Dymo embossing labeller lying around (I imagine most offices do somewhere in a back drawer) -- you know, those old gun-shaped devices that are used to make embossed adhesive labels. (Not the modern electric kind that prints on paper-thin tape, but the old-fashioned manual kind that embosses letters on thick plastic tape.)
I took a length of 1/4-inch (.64 cm) Dymo tape and stuck it on the inside cover over the metal clasp (on the left side -- not on the black magnet on the right side). The tape is thick enough to give a little fingernail room when the case is closed, and it's thick enough to drastically the strength of the magnetic. The sleepcover on/off function still works just fine, but it's a lot easier to open and close the case now.
On my Dymo labeller, pressing the spacebar trigger 15 times resulted in a piece of tape exactly the right length to stick on the magnet.
