i sent off an email to my guitar-gear-genius friend asking about the percolator. here's part of his response
"it's most definitely a one trick pony. great for that collapsing end of the world sound. there's a schematic drawn by alfonso hermida (an effects guru) somewhere out there; use that one if you want to get an exact copy."
so assuming he's right, which i generally am comfortable doing, then here ya go. DIY!
and as was already mentioned, my guy also brought up the germanium thing. "the ge trannies used are regular 1n404a which are low gain early germanium (ge). you will need both ge diodes and transistors (silicon won't work the same way) to get the real deal but you can come close with the adapted schematics attached".
i can't attach the mod versions he emailed me, but again, here's the hermida schematic.
enjoy!