A few years ago I had two selenium cells with the three wires attached custom made to mount in my dead MC meters, but I never got round to soldering them in. They were supplied by a company in England, but I forgot their name and what I paid. (80 something, but I forgot whether these were euro's or pounds).
I hope I can still find them, because I stored them away in a dark place to prevent the photons knocking electrons out of the selenium grid: this is what makes these meters work, but ultimately causes them to die.
I will be away to France untill July 25 (and hope to visit Arles!), but if you are interested, send me a PM.