Nope, you won't find a chiner frame for belted cyclocross bike.
I hope you plan a single-speed, I am against transmissions in the rear hub. The only thing that I would approve is
http://pinion.eu/en/. The transmission is in the right place, there is belt option, it has great gear range, it is weather proof & maintenance free and they have some frame options in carbon (not sure if cyclocross though).
If you find anything share the bike on the forum, it would be very interesting to see such build.