If you were to select the 2005 KTM 250 EXC from our fit guide, you'd receive the correct kit to fit your bike. It comes with all the required hardware for fitting to the handlebars and, with a little electrical work, you'll be able to wire it up to your bike's power supply.
That's because the Voyager Pro will run on any 12V power source, so if you were to wire this on the output side of your machine's voltage regulator, you'd be all set. It does have its own battery built-in, which is good for a few hours as well. For your needs, and I'm just a bit jealous of where you're riding - this device will prove a wonderful addition since, in addition to the path you've just traveled, it shows road, topography and other points of interest on its map.
I have one of these on my own bike and it has proven to be a useful tool in finding the shortest route back to the staging area when things have gone a little sideways!