http://www.stp.se/ http://www.mekanex.se/
This are some swedish companies that may help you build your gear box, I donīt think it requieres too much, I had tons of links about swedish drive and gear systems companies, but I donīt know where did I store it, otherwise, you can also, check
http://www.emachineshop.com/ is a web based company in the US that have a easy rendering software, (i can tell wonīt be difficult for you) and they will be very happy to build whatever component for your Helicopter, they actually have done it for other builders. I'm working in FEDEX in Kastrup Denmark, I may be able to help you out with the shipping...