Removed/no longer available items

So I have the old heavy shotgun both in a vending machine and in an item granter. Im trying to figure out a working method to be able to get the item into my inventory in the create menu not just when i start the game and use the vending machinr or get the item granter to give me the item like normal. I want to be able to have it in my inventory outside of the game being started so I can put it in things like item placer, item spawner, etc. I’ve looked up multiple method all seem to be from years ago when the game rule for out of bounds in creative was still a thing and involved two people with one person dropping the item outside the border and the other picking it up but that game rule has since been removed. Is there a method I can do to accomplish what I’m trying to do?