You can get the Tailgate button out of Passports or Rodeos for sure, maybe Trooper and SLX as well. So no need to make the button.
More challenging (in my experience) is getting the pigtail for the button. Most eBay sellers only sell you the switch, which is why Earl had to do the manual connections you see above. If you do find one in a yard, make sure to get the switch AND the wires.