In Eurorack you generally see 16 pin (2x8) connectors for going to the power busboard and either 16 pin or 10 pin (2x5) going to the module’s power header, depending on the module. Ribbon cables should always be made with the red stripe lining up with the little arrow indicator on the connector – this indicates pin 1 – but not every ribbon cable you may encounter has been made this way, so it’s good to double check. The other kind you may encounter is a flying busboard cable which will have a bunch of sockets on the cable for connecting other cables to (though it sounds like this might also work for your situation).
If you get an “IDC connector crimp tool” or “ribbon cable crimp tool”, a few IDC connector sizes (2x5 and 2x8 for Eurorack power), and ribbon cable (16 strand, just peel off 6 strands if you’re making a 10 pin cable connector) you can make cables to whatever specs you need for way cheaper than hunting down and buying them. For example it is often useful when powering a bunch of small modules, or when you run out of busboard headers, to make a single cable with several connectors on it rather than running separate cables to each module.
Using the crimp tool is super easy: put the connector in the shuttle that comes with the tool, feed the cable through with the red stripe lined up with the arrow, load the shuttle in the tool, squeeze. Smaller headers are also quite doable with ordinary pliers. You can find all of the above on Digikey, Sparkfun, Jameco or similar. I would probably recommend going this route for any ribbon cable needs at all beyond the cables that come with modules, rather than trying to hunt down someone selling exactly the cables you need.
