From what I understand the American market is being tested in Canada (we got them in 2007) and you might see them this or next year:
http://www.honda.ca/MCPE/Motorcycle/...Model=CBR125R8
Finding a junked bike or quad with a good tranny isn't a bad idea but it seems a little out of your budget? A bike chain won't hold up but you can get different sizes chain and sprockets for cheap at most tractor supply companies.