Someone posted a great light wiring guide over at EBR. The beauty of this circuit is that you won't need to add extra switches (unless you want to add high/low beams). The headlight/taillight relay is enabled by the 6v headlight output from your display (or switch) which in turn enables power from your battery to the converter(s). I haven't done this yet, since I'm still awaiting delivery of my new Himiway Cobra, but it's definitely ontop of my to-do list. https://electricbikereview.com/forums/threads/hunter-light-upgrade.46059/
For your particular battery voltage of 72V I would use a converter like this; https://a.co/d/cmu3YJ1
Note: The link to the brackets to mount a motorcycle headlight to your handlebars is dead but here it is. You'll want the 1.25-inch mounts. https://a.co/d/cKnmF4H