I would contact Roketa and see which one of their dealers has them in stock (and mail orders if they are not local to you).
These guys used to have them and sell them for low cost, but it appears they only have the Z50 replica. If anyone will have them, it will be these guys.
http://www.superiorpowersports.com/Motorcycle_s/136.htm
These guys have the Icebear version, which is a 3 speed semi-auto--supposed to be a decent bike from what I understand, but if you really want the 4-speed manual with clutch, this is not it.
http://www.motobuys.com/monkey-bikes.html