3/8" hose or cable clip

It uses two self drilling screws.  It's the simplest thing, but so nice to be able to quickly print and not have to shop around.  This is to hold a 3/8" OD hose.  You could use it for cables too, but consider if your thinking about holding mains voltage; this is not rated or tested for such (not recommended…).

PETG, 100% infil.  If it's not under particular stress or strain you could get away with PLA.

You can ream out the hole with a drill bit if it's not perfectly round.