Just measure the diameter of the existing round switch placement hole and go internet shopping for on/off weatherproof toggle switch that appeals (generally the vendors show pics, amp ratings, and dimensions clearly) to you. It's a metric hole so you may have to slightly enlarge it with a small rat-tail file or mechanics reamer for a good fit, and wire it to to your Headlights power source and you're done. Sorry, I'm not signed with a photo-hosting service anymore or I would send you pics.
