Good luck finding one! I ordered one for my 2001 KDX 200 two weeks ago as of yet it still hasn't been sent. If anyone knows a place that has them in stock please let me know. None of the local shops stock them as i was told they don't often break !
Any number plate off a KX will fit with a little modification, very little, regardless of whether they were intended for use with an inverted for or not. Check out the link below and have a look at the bikes in the Reader's Ride section. There are a number of bikes there with late model KX number plates.