I find this one great when you're outside of camp and all Tartarus breaks out. I just keep a little sunglasses case with all my needs in it. These include :

-my Camp Half-Blood sunglasses that protect my eyes from - up to and including - Greek fire.

- any golden dracchmma that I may have.

_ a Freddy's Frozen Custard coupon. Trust me, Freddy's is one of the only restaurants I have not gotten attacked in.

I also carry a backpack, where my sword is easily concealed.