Well, my only advise is to stay away from Kyosho Nexus. Is the worst Piece of **** heli I know. The parts on the Nexus are poor quality and spare parts are expensive......BOTOMLINE: Stay away from NEXUS

There are a lots of mail order Hobby Shops that carry Hirobo Spare Parts.
www.ronlund.com
www.heliproz.com

If they dont have it on stock, they can order it for you.

The GPH use many parts that are the same as the Hirobo Shuttle.
On the head use many parts similar to the Sceadu or Freya. So you will not have problem with spare parts.

Also, you can talk with Jeff Green at Altech wich is the company that distribute Hirobo in USA.

http://runryder.com/helicopter/f27p1/