WTB:DF 250 RTS sprockets

[commander smurf]

A new six speed counterbalanced engine is on the way to replace the stock engine on my RTS 250 along with a new chain, but I have had trouble finding sprockets for this bike. Of course the new engine has a countershaft sprocket, but I think its a 15 tooth and I'm looking for a 17/42 set up like the stock one, or maybe one tooth lower on the countershaft-does anyone know of a source for these sprockets?
Those stock chains are terrible quality-wise, they are non-O ring and mine is shot in 2,300 miles of rather hard riding (I have broken both the swing arm bolt and the frame so far). I've found that the quality of many of the Dongfang parts is awful on this bike, the plastic parts are poorly designed and made of low quality plastic, but the Zongshen engines in my Hawk and RTS have been EXCELLENT and have always run perfectly since day 1.