Instead of having the wand in one hand and your other hand empty there are a lot of options.
Staff
Staves would be alternatives to wands. The downside would be no off-hand mage item. The advantage would be casting stronger spells. Edit Suggested by @Liam_M1 Could be used as a melee weapon.
Talisman (Original Idea Talisman for Sorc)
Small items that can be held in your off-hand with a wand in your main hand. It should grant some bonus not granted by your normal gear that should only be useful to mages.
Spell Book
An item that the mage using it can write down how to cast runes inside the book. You could use the track pad to flip pages. The book wouldn’t come filled it would be hand drawn by the mage. (Example: Writing the arcane ray runes down in the book so I won’t forget in the heat of battle how to cast.)
Will update as I think of more.