How put a invisible shield into the second hand of the player?

Hello,

I'd like to improve my mod's combat system, and for defense, I had the idea of adding an invisible enchanted shield as soon as the player presses a key, G for example (although right-clicking would be better).

This invisible shield would withdraw as soon as the player stopped pressing the button.
But I don't know how to get Mcreator to add a shield to the player's second hand.

Thanks in advance!