These things are all custom designed and custom made. Bitspower and Barrow are starting to make distro blocks for popular cases, like the Lian Li O11, but even then they're a stock design so you're restricted to how they intended the loop to run or you have a load of unused channels which defeats the point.
These things are also no trivial to design either. You need to know exactly which case you're using, have sub-mm accurate measurements and know exactly what your loop order is going to be and how it all fits together, again having sub-mm accurate measurements for precisely where all your fittings and tubes will go. Then it needs building in CAD, then it needs transferring to CAM to be machined and then cleaned and assembled.
So yeah, it's an entirely bespoke job and the only people I know who are doing them are members of the modding community who are possibly too busy with their own kit to take paid commissions, even if they were comfortable doing 3rd party stuff because it's your loop, not theirs.
Now, if you can do all of the measurements, design and CAD, it's then just a case of finding somebody to CNC the thing for you. That's likely to be easier.