I just put a FMF on mine. Much better. Free Reving, and a bit snappy. One problem. LOUD!!! You also have to make some kind of fitting to hold it to the exhaust pipe, because the original has a bulge and this one doesen't
I got the Power Core IV Spark Arrestor and paid $225 for it. FMF lists it for like $270, but you'll only pay that much if you order from them. It's pretty loud. I wanted my bike to be loud to, and this exceeds my expectations. It is louder than stock with the silencer out, but with the FMF, it is the nicest sounding (and loudest) XR200 around. It's a nice looking unit, and very high quality. I would recommend it to everyone.