You can have the bars professionally cut at a bike shop or scooter shop. You could probably even find a metal shop or auto mechanic to do it for you. For those particular bars, you can even buy a reasonably price pipe cutter to cut them, but then you still have to cut a slit in them. For that, you'll need an angle grinder or a chop saw to put a 2" slit up one side. Don't use a hacksaw as the gap will be too small from the narrow blade. Try to recreate what is already there, just up a few inches, depending on how short you need to cut the bars.