We replaced our contemporary porch light with a vintage modern one purchased on Ebay. Sadly, when the light fixture arrived in the mail, the glass shade was smashed to pieces.
Rejuvenation sells vintage reproduction light fixtures and other house parts. They have a mid-century modern line called Satellite. Their Otis light is identical to the vintage 1950s light fixture we bought on Ebay. We were able to get a replacement shade through Rejuvenation and it fit perfectly in the 1950s fixture.