Why would his case need premade holes? Better yet, why would you need to even pipe it outside his case?
You, sir, are doing it wrong.
For half the price (or less) of one of those systems that mounts outside the case you can get an internally mounted pump/reservoir and swap a pair of 90/120mm casefans for coolant heatsinks. They’re cheaper, easier to install, easier to manage, easier to transport the computer with it installed, and lightyears quieter. Not to mention internal-only systems are less likely to leak and when they do leak the coolant simply pools in the bottom of the case or drains through holes you drilled instead of leaking in through the top and soaking every part you’ve got in the computer.