Metric Countersunk Sealed Plug

That countersunk profile is exactly what handles that situation. The plug seats recessed at the port face rather than protruding, so you get a clean, flush closure that won't interfere with adjacent components or clearance-tight assemblies. The M14 x 1.5 male thread matches standard metric hydraulic manifold ports, and at 16.7mm in length it's a compact fit. A 19mm wrench is all you need to drive it in with standard tooling.