I think the tachometer reading is not precise as we think... but if you look closer, the needle stands a little just below the 2000RPM, and sometimes specially when you start the engine idles a little bit higher, lets say about 2200RPM for a while then drops down.
And about the belt, there are about 3 suppliers. Dayco, Polini and Bando. Bando is the OEM supplier for the belt. sadly where i live, I can only buy original spare parts since Chinese scooters with GY6 engines dominate. But eBay always is a solution. And finally, I could not find out if the belt is shared with another scooter of another brand, if so it would be great news although I think it is possible.