well, your wrong. most nissan dealerships stock parts for imports now, they have realised the market. and i dont know where else to get a genuine belt. so ring nissan for the latest price on a genuine cam belt. lol.
genuine gt-r cam belt = $90
idler, use nissan genuine only = $250+
tensioner, use an RB30 one = $90
install, labour for mechanic around 3 hours = $130
enough for ya?