I was looking for the same remedy for my 2017 Tundra, since removing the tailgate and miss my backup camera. Probably need the camera more since adding a camper and impaired visibility. Today, I called tailagatecamera.com at 888-830-0561 and spoke with Brian, the owner. He referred me to their other website for non-tailgate camera applications, backupcameraco.com. He said he could attach an OEM Tundra harness and plug to the camera with the mount of my choice. Brian explained what he could do to accommodate my request. Impressed with his customer service.
From the backupcameraco.com website, I ordered a License Plate Lip Mount Color Camera with Hidden Mounting Bracket With MyGig Interface Harness. Once the item is added to your cart, you can add a note about the vehicle and what you need done. Sale price $99.99 ends today. Regular price $129.99. Hope this is helpful.