The only way I can think of now is to add a Tool:
1. Use menu Tools/Configure Tools....
2. Click Add in the User-defined tools dialog.
3. In the Edit Tool dialog use for cmd (without quotes): "Cmd" for Name, "cmd" for Executable and "$(TARGET_OUTPUT_DIR)" for Working directory. Leave Launching options at the first choice.
Unfortunately, macros such as $(TARGET_OUTPUT_DIR) may be working only after a build, so perhaps it would be better to hard-code the path in each tool, even if less convenient.
Now you can launch the tool via Tools menu. You can add another tool for PowerShell in the same way.
Unfortunately, I don't think it is possible to assign a keyboard shortcut for a Tool.
There is probably a better way (e.g., with scripting) but even this may be a bit faster than what are you doing now.