I’ve been looking at the Benjolin schematics. One bothersome thing is the -9 V regulator. Certainly it’s possible to buy these but they’re much scarcer than positive regulators. DigiKey has only one in THT and it’s minimum quantity 100. Mouser has one in THT. There aren’t many more options in SMD.
You could use an adjustable negative regulator but I note the TI LM337 in TO-92 packaging is end of life.
And of course you can buy TO-92 LM79L09, or at least something claimed to be that, on AliExpress or eBay but I don’t regard them as reliable vendors.
Anyway, there are options available. But I’m wondering why it’s needed in the first place.
Looking at the schematic, most of it seems it’d work with ±12 V, maybe with some adjustments to resistor values. The one thing that is problematic is the CD4021 is being powered with ±9 V, rather than the more usual positive and ground. Since the maximum supply voltage difference is 20 V, you could not use ±12 V.
Presumably the point is that the desired Rungler CV output range is ±9 V. But if that’s the case I’d think one could simply use an op amp to scale a 0 to +12 V CV to ±9 V. Then the CD4021 could be powered with +12 V and ground.
Not sure if it’s worth pursuing but it’s what I’m thinking about this morning.