The replenisher from other machines can be adapted. The unit provides 100Vac drive (japanese line voltage) to the replenisers via the three pin din socket on the back. The w/d unit also uses the replenishment signals to figure how long to run it's heater. The only 120V use in the machine is to drive the tank heaters. Otherwise there is a 120-100V large tx in one corner of the body to do the step down.
The replenishment signal is triggered from the feed in sensor bar. My sensor bar has one bad sensor, likely from the broken din socket female mate in the machine body. I have a repalcement socket to fuse in, but I am waiting for the next reason to open the machine before doing this.
I also have two variable volume 120Vac replenishment pumps salvaged from a bigish Kreonite roller processor that passed thorough my hands, but I otherwise trashed.
I have yet to mate them to the CP-31. I suspect they would run ok intermittently on 100Vac without overheating. Speed is a function of 60 cycles. I cant recall if Japan is 50 or 60 cycles. Anyways, I am pretty sure the replnishment module form fujimoto worked with the CP -3x and 5x, and for the bigger unit you just set the cam to provide more volume drive to the pump piston.
Unless you are runnig a lot of prints, I would not worry about the replenisher. I run Kodak RA-RT, and it calls for 20mL per 8x10. Mostly I print 8x10. I tend to pull the top cover ajar, and pour in 80mL after 4 prints have gone though and none are mid way though the machine. I see no variability in print density or quality using this practice.