Extremely hard to find these in good shape as they were plastic which only lasts so long, coupled with the fact that the backsides of them were hammered by gravel, salt etc. The plastic that accepts the mounting brackets are almost always broken and the exposed "chrome" peeled off.
I've dabbled in finding reverse lights from other cars that might be a solution, but without success. End result is that I've taken those that I've accumulated over the years, determined which have the best exposed surfaces complete with lenses... and secured them with caulking. My suggestion would be not to expect perfection in any that you find. (Or get a 3D printer...)