I personally think you should get it from HP. There are others like Ebay for example. A bad battery can explode, not that I seem one explode before. To save a few bucks for a $1500 laptop is not worth it.
If you don't need the battery now, you can wait a little. Before HP retires your model, they sometime put all the accessories for your model on sale. I got my Zt3000 battery for $75 from HP. Two weeks later, HP stop selling the Zt3000. It was on sale plus free shipping. Also use Fatwallet for another 4-5% cash back.