Standard Minki pockets are meant to be good overnight, although we don't use them (I have a Slinki Minki we use during the day though and that works well). The stuffing you'll need depends on how heavily your LO wets. Natural and manmade fibers hold liquid differently (within vs between fibers), so a combination often works well - we use microfibre on top of hemp. But it really is down to trial and error as to what works best for you. Easy Peasy hemp inserts are nice and cheap and you can pick up MF cloths in supermarkets. Otherwise something like a Fuzzi Bunz insert works for us, too.
As for other night nappies, we use two parters rather than pockets overnight: Baby Beehinds bamboo fleece, Ella's House Bumhuggers, Swaddlebees Organic Velour One-Size and a Holden's Landing BedBug. They can all last for about 11 hours, although I do usually top-up the absorbancy by adding more hemp (Iris can be a heavy wetter). And I always add a fleece liner to help her to feel dry overnight (a cheapo fleece baby blanket cut to size to completely cover the nappy works a treat).
There's a wanted section here, too, as well as the sale classifieds.