Swapping an item with an npc-only item m2?

[Goraja]

I found the m2 and blp for Cairne Bloodhoof's totem weapon and would like to put it on an ingame 2H mace. Is this possible? ModelSwapper will unfortunately only take a model from an item available in-game to players. If it makes any difference, this is on a private trinity server that I operate.

If this can be done manually, I will crawl in and edit MPQs etc. I just can't find any item tutorials that don't use ModelSwapper. Thanks!