Are you looking to get rid of the headlight? If so order UFO part number 12-521-29 for a front number plate. If you are goint to keep the odometer you'll need to raise it 1/4 inch to clear the number plate. You'll also need to make a small plate for the two bottom bolts.
After smashing the odometer several times, and crushing 2 headlights in HS races, I put on a '01 KX250/125 front plate. I had to cut it a little, and it sits a little above the front fender, but it looks good and has stood up well after about a dozen encounters with large woody biomass. I've seen people at the races that have had older style #plates which fit the fender a little better, but they seem to make any KDX look like pre- 1995 vintage at first glance. I also saw a racer that had mounted a vented #plate on his KDX so well that it looked like an OEM part (not sure what Co. made the plate).