I didn't even check yet, but the original creator mentioned they got all the parts from Tayda - they seem to be out of stock now, but I think I have some from a previous order, and
https://www.taydaelectronics.com/photo-conductive-cell-resistor-ldr-540nm-radial.html is probably also suitable. I might put in sockets and try the vactrols I got from Aliexpress a while back (used for General Tso for example).
I don't even have the PCB's yet, no word on drill template from the creator, so I'll probably have to measure it myself so it will still take weeks until I can get it built.
I did receive the spring tank already though.