Many years ago, Raytheon made one, probably not available anymore. You can make your own with an LDR and lamp or LED in a tube (cut a section out of a ball point pen). The lamp will give better control than the LED.
They were always a VERY obscure devices - essentially used for audio uses, AGC, guitar effects, things like that - so I would have thought the number of manufacturers was tiny?.
But it's hardly a 'component', it's just an LDR and a bulb (or LED) with a bit of black shrinkwrap around them.
Clairex (https://www.clairex.com) used to be a biggie in the manufacture of analog optocouplers. I was surprised to find that they had a Web address. I thought that they were the St. Louis based company that was bought out by Perkin-Elmer. Maybe they've split them off again. I dunno. I have a databook in storage somewhere that shows the really nifty product line that Clairex had during the 1980s. As Nigel says, things like that are easy builds for one-of-a-kind projects but would not be practical if you're intending to make 1000 or more of something. The trick is to make sure that your assembly is absolutely light-tight. The teensiest light leak can be detected by an LDR, not really unexpected, considering that their resistance move can often be from under 100 ohms to over 100M ohms.