Well, the least you can do is ask these guys for the price of a complete engine:
http://www.skyteammotor.com/Home/
Here in Bulgaria for example we have one dealer of Chinese parts, who sells a similar engine for ~500eur
http://motobg.net/ocart/%D0%B4%D0%B2...0%BC3-sku-1593
I know that's like half of what the bike's worth, but it's inevitable when you're facing a complete engine transplant.