If you are using Blocks (not InterfaceBlocks) to Type your Ports just use "manual" feature-by feature direction inversion to achieve type conjugation (and you can even use a ~ tilde prefix)
In fact, some SysML users already used the ~ tilde prefix for conjugated types long before the SysML-1.6 ~InterfaceBlock was introduced.
Just don't stereotype your "manual" conjugate as an «~interfaceBlock»!