for the Keyence parts, I put the part numbers in the text for you.
Keyence amplifier LV-11SB
Keyence laser assembly LV-S62
I got mine on ebay
about detecting frame lines, I can speculate that it is a stack of sensors reading the density of the film from one position to the next across the entire frame. It is kinda the opposite of detecting the sprocket holes. You set the scan device to find the blackest (or clearest) part of the film all along the frameline. You should be able to use a stack of the keyence sensors and average the output. Since they can be calibrated to look for the condition you want, it may/could work.