Best range extender for Nighthawk AC1900

Netgear has a lot of range extenders. I usually push people towards the tri-band extenders because they have higher throughput and lower latency due to their dedicated backhaul. 

But basically, pick what features you want in an extender and that match your budget. 

https://www.netgear.com/home/products/networking/wifi-range-extenders/