There are at least a couple vendors with self-contained liquid cooling systems, kind of like the “all-in-one” systems available for desktop and gaming use. I don’t know how effective they are.
You're right and while it might take up valuable rack space I would imagine there are some rack-based solutions that have most of the stuff included so that you don't have to rely on the dc providing it, pretty sure ServeTheHome has done a couple reports on them