As Cam says, the Nulon is fine, but I found 2 x 5lt bottles of Nissan Matic J was actually cheaper than 3 x 4lt bottles of Nulon, or even 2 x 4lt + 2 x 1lt.
You need around 9lt for a full flush so you'll also have a little left for top ups later. I'd do the sums first, but frankly a small difference in price wouldn't be enough for me to go away from the OEM..