what I did...
I have exact same bike. Love it, but wanted accurate speedometer. Working in bicycle shop, I grabbed a Sigma bicycle computer, extended the sensor wire and mounted it to CBR.
Little magnet that fits inside one of the front rotor bolt heads. Sensor safety wired onto fork leg. Wire up behind fender and up front brake line. Head/readout unit mounted near key. Works great!
Use Sigma because they don't have a roll-over point (some bike computers only go to 70 mph or so...) and they used to be stock gauge "upgrade" on KTM bikes. Model I have displays current speed, average speed, maximum speed !!!, time of day, stopwatch, trip distance and total distance. Because you calibrate it yourself (easy), you can get wheel's rolling circumfrence down to the millimeter exact.
Mine has proven the stock speedo to be 7-8mph optomistic. The only thing the Sigma does not have is a light at night, but I have an idea for that fix as well.
Email me directly if you need a picture or if you want a computer to do your own. Best part is the price, only $40 plus a scrap of wire and maybe another magnet. Totally cheap and much more accurate info than stock equipment would be.