Is there a way to add 3D items using just their item ID? I really want to look at some things but only one person owns them and I don't know who it is...

Simple google search.
http://forum.toribash.com/showthread.php?t=492531

I mean items that are already in the game, I was trying to see if I could look at
2115: Muay Thai Left Foot
2116: Muay Thai Right Foot
2117: Muay Thai head band
2118: Muay Thai Left Armband
2119: Muay Thai Right Armband
2120: Muay Thai Left Hand
2121: Muay Thai Right Hand
Edit: a way to find out who owns them might work too.

Yeh i also wanna see this chrome dome item shmevin owns it i know that hut its in his deac

This tutorial might be what you were looking for.