You can still get the Doepfer PSU3.
Or TipTop Studio Buses. Though you’ll need a lot of them since they’re a bit low power.
It’s really too bad the Malekko boards appear to be extinct though. I wonder if they could be open sourced and/or the design adapted for DIY-ability?
Came across this nugget while searching for info on my own power needs recently. Totally overkill for me, but might be relevant to your large case: