From P914 Website:
The Domeless Light
Porsche 914 and Porsche 914/6 vehicles contain an interior light manufactured by Hella, This lamp has an off-white three-setting switch with positions for off, on and door-switch activation. Because of the removable roof, the interior light fits into the center section of the back pad located behind the seats. The lens sits nearly flush with the pad when installed, so terming it a "dome light" really makes no sense.
The factory-provided interior lights in the Porsche 914 models possess a chrome trim and were (not surprisingly) "Made In Germany." The OEM replacements are currently "Hecho en Mexico," do not have the chrome found on the factory provided units and have a black switch. This is unfortunate, because the majority of original Porsche 914 and 914/6 interior lights have suffered bulb heat, water or other damage during decades of use. As such, original examples in good condition have become extremely hard to obtain.
Current eBay listings for Porsche 914 interior lights (compare listed items with those pictured on this page to ensure authenticity and/or suitability.)
http://www.p914.com/p914_lenses_interior.htm