You can make a silencer from a '89 - mid '90's KDX200 to fit with some slight modifications and by making an additional short sleeve to connect the silencer with the end of your exhaust pipe. Only one of the two mounting bolt positions on your frame will line up with the silencer, though.
I had an Answer silencer/spark arrestor for a KDX200 on my old 250. Not only will was it much lighter, but it will smoothed the low rpm hit of the stock silencer up some in the rpm range.