Let's see. First up: quote from the Boeing Co. website:
"The Boeing 737-900ER is the newest member of the Next-Generation 737 airplane family. The higher capacity, longer-range derivative of the 737-900 was launched on July 18, 2005 with an order for 30 airplanes from Indonesia's Lion Air."
Second: Quote from airliners.net:
"A higher gross weight longer range version is offered. It features increased fuel capacity, and strengthened undercarriage and structures, but is otherwise identical to the standard 737-400."
I'll give you one thing, they aren't actually named ER or HGW (officially, that is) so it's hard if not impossible to find a 734ER registration.