The whole point of keeping the mystical nature of a GM, well... mystical is that they don't show up with bad ass gear and strike down uber players and mobs with their awesome gear. I would liken a GM to John Travolta when he played the Shylock in "Get Shorty". You say as little as you have to, if anything at all.
Basically if you are doing your job as a GM you are not there to flaunt your power in front of the masses and right click items to get the job done. You are there to resolve issues with the server or coordinate events and such. Your Guides are going to do the majority of the major conversations for dispute resolution and things like that.
When you #GM ON you render yourself invulnerable anyhow, making any gear unnecessary. The gear GMs and Guides wear all have helping properties. They are not all that special. There are a few that are a bit OP, but again, you really dont need a 700 DMG clickie when you can just type #kill.
Here are some links to the guide items:
Exquisite Violet...
...of Humility
As you can see, all of the item effects are the same for the specific slot, they are just different colors and type of armor for different classes.
The Quartermaster in Sunset Home sells the other items. Here is that list:
Quartermaster