Nyko’s Power Grip Pro, the first third-party 3DS Circle Pad Pro accessory. This thing is important because Nintendo’s official accessory is super hard to find – although that fact suggests that maybe it won’t be necessary for many games.
Unlike the official model, this $30 accessory also includes an extra battery pack, which promises “up to 3x the playtime.” Nice! It’ll ship in October, just a few months after I bought this other Nyko battery. :(