I've done the 450 exhaust on a 350X thing before and his year when we bought the 200x it came with some POS Kerker or Cobra/DG thing that did nothing but make noise. It was a straight thru megaphone with no spark arrestor so it wouldn't cut it for us as we ride in MI where you need a spark arrestor. I was heading down the "find an OEM replacement path" but to find one complete and in really good shape was a small fortune. I borrowed a stock TRX 450 from Tapper and started to think about that and it seemed really quite a simple retrofit, so that is the direction we would go. I fell into this White Bros system for a TRX 450 locally for $100 and that is what we used. the OD of the stock 200X header and the ID of the 450 header are close enough that a clamp would work. I decided to cut both for about a 1"overlap and weld the two together. Definitely simpler and much easier than modifying it for the 350X, the angles are almost perfectly the same, pipes line up perfectly. Came with the spark arrestor insert and sounds perfect.
Video of it running.....
http://youtu.be/yD_zf2lu6A8