Even the authentic appearing shine-up (or the older shine-down) replica license plate light fixtures are not only very expensive but prone to leaking. Whereas a sensible and attractive option is a Ghia shine-down light housing such as Marty (and many others) have. They're frequently available on TheSamba for about $30.
So they're NOT authentic...so what?...neither is the fake replica they're driving!
Carl, the Karmen Ghia Shinedown license plate light is close but I'm running the 550 Spyder Shinedown. The Ghia option looks good too and is a much more economical option.